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    <title>DEV Community: Lilury</title>
    <description>The latest articles on DEV Community by Lilury (@lilury).</description>
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      <title>🏗️ Building a Clean Architecture API with Go, Ore, and SQLite</title>
      <dc:creator>Firas M. Darwish</dc:creator>
      <pubDate>Sat, 07 Mar 2026 17:10:00 +0000</pubDate>
      <link>https://dev.to/lilury/building-a-clean-architecture-api-with-go-ore-and-sqlite-4ilf</link>
      <guid>https://dev.to/lilury/building-a-clean-architecture-api-with-go-ore-and-sqlite-4ilf</guid>
      <description>&lt;p&gt;So you've been writing Go for a bit. Your &lt;code&gt;main.go&lt;/code&gt; is growing. You've got a database call next to an HTTP handler next to a business rule, and somewhere in the back of your head a little voice keeps whispering &lt;em&gt;"this is going to be a nightmare to test."&lt;/em&gt;&lt;/p&gt;

&lt;p&gt;That voice is right. And today we're going to silence it. 🤫&lt;/p&gt;

&lt;p&gt;We're going to build a &lt;strong&gt;Book Library REST API&lt;/strong&gt; from scratch using &lt;strong&gt;Clean Architecture&lt;/strong&gt; - a layered design that keeps your business logic completely isolated from databases, HTTP frameworks, and anything else that changes for the wrong reasons. To wire it all together, we'll use &lt;strong&gt;&lt;a href="https://ore.lilury.com" rel="noopener noreferrer"&gt;Ore&lt;/a&gt;&lt;/strong&gt;, a lightweight dependency injection container for Go. And for persistence, we'll use &lt;strong&gt;SQLite&lt;/strong&gt; via the &lt;code&gt;modernc.org/sqlite&lt;/code&gt; driver (pure Go, no CGo required - your CI pipeline will thank you 🙏).&lt;/p&gt;

&lt;p&gt;By the end of this guide you'll have:&lt;/p&gt;

&lt;ul&gt;
&lt;li&gt;📦 A proper 4-layer Clean Architecture project structure&lt;/li&gt;
&lt;li&gt;🗄️ A real SQLite database with schema migration on startup&lt;/li&gt;
&lt;li&gt;💉 Ore managing all dependency wiring, lifetimes, and startup validation&lt;/li&gt;
&lt;li&gt;🔌 Graceful shutdown that closes the DB connection cleanly&lt;/li&gt;
&lt;/ul&gt;

&lt;p&gt;Let's go.&lt;/p&gt;




&lt;h2&gt;
  
  
  🗺️ The Big Picture
&lt;/h2&gt;

&lt;p&gt;Before writing a single line of code, let's understand &lt;em&gt;why&lt;/em&gt; Clean Architecture matters.&lt;/p&gt;

&lt;p&gt;The core rule is simple: &lt;strong&gt;dependencies only point inward.&lt;/strong&gt; The domain layer (your business rules) knows nothing about HTTP or SQLite. The application layer (your use cases) knows the domain but not the database driver. Infrastructure (your SQLite repo) knows the domain interface it implements, but the domain doesn't know SQLite exists.&lt;br&gt;
&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;┌──────────────────────────────────────────────┐
│              Presentation (HTTP)              │  ← knows application
├──────────────────────────────────────────────┤
│           Application (Use Cases)            │  ← knows domain
├──────────────────────────────────────────────┤
│          Domain (Entities + Interfaces)       │  ← knows nothing
├──────────────────────────────────────────────┤
│         Infrastructure (SQLite, etc.)         │  ← knows domain interfaces
└──────────────────────────────────────────────┘
         ↑ Dependencies point inward ↑
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;p&gt;What makes this possible in Go is &lt;strong&gt;interfaces&lt;/strong&gt;. The domain defines &lt;code&gt;BookRepository&lt;/code&gt; as an interface. The infrastructure provides the concrete SQLite implementation. The application layer depends only on the interface. Ore acts as the &lt;strong&gt;composition root&lt;/strong&gt; - the one place that says "okay, when someone needs a &lt;code&gt;BookRepository&lt;/code&gt;, give them the SQLite one."&lt;/p&gt;

&lt;p&gt;Here's the project layout we'll build:&lt;br&gt;
&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;booklib/
├── main.go
├── go.mod
├── domain/
│   └── book.go           # Entity + repository interface
├── application/
│   └── book_service.go   # Use cases
├── infrastructure/
│   └── sqlite_repo.go    # SQLite repository implementation
├── presentation/
│   └── book_handler.go   # HTTP handlers + route registration
└── di/
    └── container.go      # 🎯 The composition root - all Ore wiring lives here
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;p&gt;Notice &lt;code&gt;di/container.go&lt;/code&gt; is the only file that imports all layers at once. Every other package stays in its lane.&lt;/p&gt;




&lt;h2&gt;
  
  
  ⚙️ Step 1: Initialize the Project
&lt;/h2&gt;



&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight shell"&gt;&lt;code&gt;&lt;span class="nb"&gt;mkdir &lt;/span&gt;booklib &lt;span class="o"&gt;&amp;amp;&amp;amp;&lt;/span&gt; &lt;span class="nb"&gt;cd &lt;/span&gt;booklib
go mod init booklib

&lt;span class="c"&gt;# Ore for dependency injection&lt;/span&gt;
go get &lt;span class="nt"&gt;-u&lt;/span&gt; github.com/firasdarwish/ore

&lt;span class="c"&gt;# Pure-Go SQLite driver - no CGo, no drama&lt;/span&gt;
go get modernc.org/sqlite
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;blockquote&gt;
&lt;p&gt;💡 &lt;strong&gt;Why &lt;code&gt;modernc.org/sqlite&lt;/code&gt; over &lt;code&gt;mattn/go-sqlite3&lt;/code&gt;?&lt;/strong&gt; The &lt;code&gt;mattn&lt;/code&gt; driver requires CGo, which complicates cross-compilation and Docker builds. &lt;code&gt;modernc.org/sqlite&lt;/code&gt; is a pure Go port - it compiles and runs anywhere Go does.&lt;/p&gt;
&lt;/blockquote&gt;




&lt;h2&gt;
  
  
  🧠 Step 2: The Domain Layer - The Heart of the App
&lt;/h2&gt;

&lt;p&gt;The domain layer is sacred. It contains your business entities and the &lt;em&gt;contracts&lt;/em&gt; (interfaces) that describe what the app needs from the outside world. &lt;strong&gt;No imports from other layers. No Ore. No &lt;code&gt;database/sql&lt;/code&gt;. Nothing.&lt;/strong&gt;&lt;br&gt;
&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="c"&gt;// domain/book.go&lt;/span&gt;
&lt;span class="k"&gt;package&lt;/span&gt; &lt;span class="n"&gt;domain&lt;/span&gt;

&lt;span class="k"&gt;import&lt;/span&gt; &lt;span class="s"&gt;"errors"&lt;/span&gt;

&lt;span class="c"&gt;// Book is our core entity. It belongs to the domain, not to any database table.&lt;/span&gt;
&lt;span class="k"&gt;type&lt;/span&gt; &lt;span class="n"&gt;Book&lt;/span&gt; &lt;span class="k"&gt;struct&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;ID&lt;/span&gt;     &lt;span class="kt"&gt;int64&lt;/span&gt;
    &lt;span class="n"&gt;Title&lt;/span&gt;  &lt;span class="kt"&gt;string&lt;/span&gt;
    &lt;span class="n"&gt;Author&lt;/span&gt; &lt;span class="kt"&gt;string&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="c"&gt;// These are domain errors - they describe business-level failures,&lt;/span&gt;
&lt;span class="c"&gt;// not HTTP status codes or SQL error codes.&lt;/span&gt;
&lt;span class="k"&gt;var&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;
    &lt;span class="n"&gt;ErrBookNotFound&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="n"&gt;errors&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;New&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"book not found"&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="n"&gt;ErrInvalidBook&lt;/span&gt;  &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="n"&gt;errors&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;New&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"book title and author are required"&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
&lt;span class="p"&gt;)&lt;/span&gt;

&lt;span class="c"&gt;// BookRepository is the contract the domain needs from persistence.&lt;/span&gt;
&lt;span class="c"&gt;// It doesn't know or care that SQLite is on the other side.&lt;/span&gt;
&lt;span class="c"&gt;// Tomorrow it could be Postgres. The domain layer would never know.&lt;/span&gt;
&lt;span class="k"&gt;type&lt;/span&gt; &lt;span class="n"&gt;BookRepository&lt;/span&gt; &lt;span class="k"&gt;interface&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;Save&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;book&lt;/span&gt; &lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="kt"&gt;error&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="n"&gt;FindByID&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;id&lt;/span&gt; &lt;span class="kt"&gt;int64&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="kt"&gt;error&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="n"&gt;FindAll&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt; &lt;span class="p"&gt;([]&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="kt"&gt;error&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;p&gt;This is the most important file in the project - and it has zero external dependencies. That's the point. Your business rules don't need SQLite to exist. They don't need &lt;code&gt;net/http&lt;/code&gt; to exist. They just need a &lt;code&gt;BookRepository&lt;/code&gt; that works.&lt;/p&gt;




&lt;h2&gt;
  
  
  🔧 Step 3: The Application Layer - Where Use Cases Live
&lt;/h2&gt;

&lt;p&gt;The application layer orchestrates your use cases. It takes user intentions ("create a book"), applies domain rules (validate input), delegates to the repository (persist it), and returns results. It knows the domain package. It does &lt;strong&gt;not&lt;/strong&gt; know SQLite, HTTP, or anything infrastructure-related.&lt;br&gt;
&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="c"&gt;// application/book_service.go&lt;/span&gt;
&lt;span class="k"&gt;package&lt;/span&gt; &lt;span class="n"&gt;application&lt;/span&gt;

&lt;span class="k"&gt;import&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;
    &lt;span class="s"&gt;"booklib/domain"&lt;/span&gt;
    &lt;span class="s"&gt;"context"&lt;/span&gt;

    &lt;span class="s"&gt;"github.com/firasdarwish/ore"&lt;/span&gt;
&lt;span class="p"&gt;)&lt;/span&gt;

&lt;span class="c"&gt;// BookService contains all the use cases for the book feature.&lt;/span&gt;
&lt;span class="k"&gt;type&lt;/span&gt; &lt;span class="n"&gt;BookService&lt;/span&gt; &lt;span class="k"&gt;struct&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;repo&lt;/span&gt; &lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;BookRepository&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="c"&gt;// NewBookService is Ore's initializer for this service.&lt;/span&gt;
&lt;span class="c"&gt;// Notice it asks Ore for domain.BookRepository - an interface.&lt;/span&gt;
&lt;span class="c"&gt;// It has no idea that SQLite is behind it. 🤷&lt;/span&gt;
&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="n"&gt;NewBookService&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;ctx&lt;/span&gt; &lt;span class="n"&gt;context&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Context&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;BookService&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;context&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Context&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;repo&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;ctx&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Get&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;BookRepository&lt;/span&gt;&lt;span class="p"&gt;](&lt;/span&gt;&lt;span class="n"&gt;ctx&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;BookService&lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="n"&gt;repo&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt; &lt;span class="n"&gt;repo&lt;/span&gt;&lt;span class="p"&gt;},&lt;/span&gt; &lt;span class="n"&gt;ctx&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="c"&gt;// CreateBook validates input and persists a new book.&lt;/span&gt;
&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;s&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;BookService&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="n"&gt;CreateBook&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;title&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;author&lt;/span&gt; &lt;span class="kt"&gt;string&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="kt"&gt;error&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;title&lt;/span&gt; &lt;span class="o"&gt;==&lt;/span&gt; &lt;span class="s"&gt;""&lt;/span&gt; &lt;span class="o"&gt;||&lt;/span&gt; &lt;span class="n"&gt;author&lt;/span&gt; &lt;span class="o"&gt;==&lt;/span&gt; &lt;span class="s"&gt;""&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;{},&lt;/span&gt; &lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ErrInvalidBook&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;
    &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;s&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;repo&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Save&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="n"&gt;Title&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt; &lt;span class="n"&gt;title&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;Author&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt; &lt;span class="n"&gt;author&lt;/span&gt;&lt;span class="p"&gt;})&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="c"&gt;// GetBook retrieves a book by its ID.&lt;/span&gt;
&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;s&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;BookService&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="n"&gt;GetBook&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;id&lt;/span&gt; &lt;span class="kt"&gt;int64&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="kt"&gt;error&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;s&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;repo&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;FindByID&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;id&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="c"&gt;// ListBooks returns all books in the library.&lt;/span&gt;
&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;s&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;BookService&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="n"&gt;ListBooks&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt; &lt;span class="p"&gt;([]&lt;/span&gt;&lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="kt"&gt;error&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;s&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;repo&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;FindAll&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;p&gt;The &lt;code&gt;NewBookService&lt;/code&gt; initializer is doing something subtle but powerful: &lt;code&gt;ore.Get[domain.BookRepository](ctx)&lt;/code&gt; asks Ore to resolve the &lt;code&gt;BookRepository&lt;/code&gt; interface from the dependency graph. At this point in the code, we have absolutely no idea what the concrete type is. The DI container (&lt;code&gt;di/container.go&lt;/code&gt;) will decide that later.&lt;/p&gt;




&lt;h2&gt;
  
  
  🗄️ Step 4: The Infrastructure Layer - SQLite Gets Its Hands Dirty
&lt;/h2&gt;

&lt;p&gt;Now for the fun part. The infrastructure layer is where we actually talk to SQLite. This package knows it's implementing &lt;code&gt;domain.BookRepository&lt;/code&gt;. It knows about &lt;code&gt;database/sql&lt;/code&gt;. It knows about SQL queries. The domain and application layers remain blissfully unaware of all this.&lt;br&gt;
&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="c"&gt;// infrastructure/sqlite_repo.go&lt;/span&gt;
&lt;span class="k"&gt;package&lt;/span&gt; &lt;span class="n"&gt;infrastructure&lt;/span&gt;

&lt;span class="k"&gt;import&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;
    &lt;span class="s"&gt;"booklib/domain"&lt;/span&gt;
    &lt;span class="s"&gt;"context"&lt;/span&gt;
    &lt;span class="s"&gt;"database/sql"&lt;/span&gt;
    &lt;span class="s"&gt;"errors"&lt;/span&gt;
    &lt;span class="s"&gt;"log"&lt;/span&gt;

    &lt;span class="s"&gt;"github.com/firasdarwish/ore"&lt;/span&gt;
    &lt;span class="n"&gt;_&lt;/span&gt; &lt;span class="s"&gt;"modernc.org/sqlite"&lt;/span&gt; &lt;span class="c"&gt;// registers the "sqlite" driver&lt;/span&gt;
&lt;span class="p"&gt;)&lt;/span&gt;

&lt;span class="c"&gt;// DB is a thin wrapper around *sql.DB so Ore can manage its lifetime&lt;/span&gt;
&lt;span class="c"&gt;// as a distinct type in the container.&lt;/span&gt;
&lt;span class="k"&gt;type&lt;/span&gt; &lt;span class="n"&gt;DB&lt;/span&gt; &lt;span class="k"&gt;struct&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;sql&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;DB&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="c"&gt;// NewDB opens the SQLite connection and runs schema migrations.&lt;/span&gt;
&lt;span class="c"&gt;// Registered as a Singleton - one DB pool for the entire app lifetime.&lt;/span&gt;
&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="n"&gt;NewDB&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;ctx&lt;/span&gt; &lt;span class="n"&gt;context&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Context&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;DB&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;context&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Context&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;sqlDB&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;sql&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Open&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"sqlite"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="s"&gt;"./books.db"&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="n"&gt;log&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Fatalf&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"❌ failed to open SQLite: %v"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;

    &lt;span class="c"&gt;// Tune the connection pool for SQLite's single-writer model&lt;/span&gt;
    &lt;span class="n"&gt;sqlDB&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;SetMaxOpenConns&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="m"&gt;1&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="n"&gt;sqlDB&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;SetMaxIdleConns&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="m"&gt;1&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;

    &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;sqlDB&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Ping&lt;/span&gt;&lt;span class="p"&gt;();&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="n"&gt;log&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Fatalf&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"❌ SQLite ping failed: %v"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;

    &lt;span class="c"&gt;// Run schema migration - create the table if it doesn't exist&lt;/span&gt;
    &lt;span class="n"&gt;_&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="n"&gt;sqlDB&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Exec&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;`
        CREATE TABLE IF NOT EXISTS books (
            id     INTEGER PRIMARY KEY AUTOINCREMENT,
            title  TEXT    NOT NULL,
            author TEXT    NOT NULL
        )
    `&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="n"&gt;log&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Fatalf&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"❌ failed to run migrations: %v"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;

    &lt;span class="n"&gt;log&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Println&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"✅ SQLite connected and schema ready"&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;DB&lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="n"&gt;sqlDB&lt;/span&gt;&lt;span class="p"&gt;},&lt;/span&gt; &lt;span class="n"&gt;ctx&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="c"&gt;// Shutdown closes the database connection.&lt;/span&gt;
&lt;span class="c"&gt;// Ore will call this at application exit via GetResolvedSingletons[Shutdowner]().&lt;/span&gt;
&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;db&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;DB&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="n"&gt;Shutdown&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;log&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Println&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"🔌 Closing SQLite connection..."&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;db&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Close&lt;/span&gt;&lt;span class="p"&gt;();&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="n"&gt;log&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Printf&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"⚠️  error closing DB: %v"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="c"&gt;// SQLiteBookRepository is the concrete implementation of domain.BookRepository.&lt;/span&gt;
&lt;span class="k"&gt;type&lt;/span&gt; &lt;span class="n"&gt;SQLiteBookRepository&lt;/span&gt; &lt;span class="k"&gt;struct&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;db&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;DB&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="c"&gt;// NewSQLiteBookRepository is Ore's initializer for the repository.&lt;/span&gt;
&lt;span class="c"&gt;// It resolves *DB from the container - Ore ensures it's the same singleton instance.&lt;/span&gt;
&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="n"&gt;NewSQLiteBookRepository&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;ctx&lt;/span&gt; &lt;span class="n"&gt;context&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Context&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;SQLiteBookRepository&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;context&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Context&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;db&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;ctx&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Get&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;DB&lt;/span&gt;&lt;span class="p"&gt;](&lt;/span&gt;&lt;span class="n"&gt;ctx&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;SQLiteBookRepository&lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="n"&gt;db&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt; &lt;span class="n"&gt;db&lt;/span&gt;&lt;span class="p"&gt;},&lt;/span&gt; &lt;span class="n"&gt;ctx&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;r&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;SQLiteBookRepository&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="n"&gt;Save&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;book&lt;/span&gt; &lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="kt"&gt;error&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;result&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;r&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;db&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Exec&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;
        &lt;span class="s"&gt;"INSERT INTO books (title, author) VALUES (?, ?)"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
        &lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Title&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Author&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
    &lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;{},&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;
    &lt;span class="n"&gt;id&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;result&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;LastInsertId&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;
    &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;{},&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;
    &lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ID&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="n"&gt;id&lt;/span&gt;
    &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;r&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;SQLiteBookRepository&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="n"&gt;FindByID&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;id&lt;/span&gt; &lt;span class="kt"&gt;int64&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="kt"&gt;error&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;row&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;r&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;db&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;QueryRow&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"SELECT id, title, author FROM books WHERE id = ?"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;id&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="k"&gt;var&lt;/span&gt; &lt;span class="n"&gt;book&lt;/span&gt; &lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;
    &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;row&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Scan&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ID&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Title&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Author&lt;/span&gt;&lt;span class="p"&gt;);&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;errors&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Is&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;err&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;sql&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ErrNoRows&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
            &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;{},&lt;/span&gt; &lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ErrBookNotFound&lt;/span&gt;
        &lt;span class="p"&gt;}&lt;/span&gt;
        &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;{},&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;
    &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;r&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;SQLiteBookRepository&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="n"&gt;FindAll&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt; &lt;span class="p"&gt;([]&lt;/span&gt;&lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="kt"&gt;error&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;rows&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;r&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;db&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Query&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"SELECT id, title, author FROM books ORDER BY id ASC"&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;
    &lt;span class="k"&gt;defer&lt;/span&gt; &lt;span class="n"&gt;rows&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Close&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;

    &lt;span class="k"&gt;var&lt;/span&gt; &lt;span class="n"&gt;books&lt;/span&gt; &lt;span class="p"&gt;[]&lt;/span&gt;&lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;
    &lt;span class="k"&gt;for&lt;/span&gt; &lt;span class="n"&gt;rows&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Next&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="k"&gt;var&lt;/span&gt; &lt;span class="n"&gt;book&lt;/span&gt; &lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Book&lt;/span&gt;
        &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;rows&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Scan&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ID&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Title&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Author&lt;/span&gt;&lt;span class="p"&gt;);&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
            &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt;
        &lt;span class="p"&gt;}&lt;/span&gt;
        &lt;span class="n"&gt;books&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="nb"&gt;append&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;books&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;
    &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="n"&gt;books&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;rows&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Err&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;p&gt;A few design decisions worth calling out:&lt;/p&gt;

&lt;p&gt;The &lt;code&gt;DB&lt;/code&gt; wrapper type exists so that Ore can track &lt;code&gt;*DB&lt;/code&gt; as a distinct named type in the container. Without the wrapper, we'd be registering &lt;code&gt;*sql.DB&lt;/code&gt; - which is fine, but less descriptive and harder to extend later (e.g. if you wanted to add health check methods).&lt;/p&gt;

&lt;p&gt;&lt;code&gt;SetMaxOpenConns(1)&lt;/code&gt; is important for SQLite. It's a file-based, single-writer database - opening many concurrent connections is counterproductive and can cause locking errors. One connection, properly managed, is the right call.&lt;/p&gt;

&lt;p&gt;The &lt;code&gt;Shutdown()&lt;/code&gt; method is our exit hook. Ore will find this automatically when we call &lt;code&gt;ore.GetResolvedSingletons[Shutdowner]()&lt;/code&gt; in &lt;code&gt;main.go&lt;/code&gt;.&lt;/p&gt;




&lt;h2&gt;
  
  
  🌐 Step 5: The Presentation Layer - HTTP Talks to the World
&lt;/h2&gt;

&lt;p&gt;The presentation layer handles the HTTP surface of the app. It speaks JSON in, JSON out. It knows the application layer (to call use cases) but nothing about SQLite, domain errors beyond what it needs to map, or any infrastructure concern.&lt;br&gt;
&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="c"&gt;// presentation/book_handler.go&lt;/span&gt;
&lt;span class="k"&gt;package&lt;/span&gt; &lt;span class="n"&gt;presentation&lt;/span&gt;

&lt;span class="k"&gt;import&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;
    &lt;span class="s"&gt;"booklib/application"&lt;/span&gt;
    &lt;span class="s"&gt;"booklib/domain"&lt;/span&gt;
    &lt;span class="s"&gt;"context"&lt;/span&gt;
    &lt;span class="s"&gt;"encoding/json"&lt;/span&gt;
    &lt;span class="s"&gt;"errors"&lt;/span&gt;
    &lt;span class="s"&gt;"net/http"&lt;/span&gt;
    &lt;span class="s"&gt;"strconv"&lt;/span&gt;

    &lt;span class="s"&gt;"github.com/firasdarwish/ore"&lt;/span&gt;
&lt;span class="p"&gt;)&lt;/span&gt;

&lt;span class="c"&gt;// BookHandler holds all the HTTP handler methods for books.&lt;/span&gt;
&lt;span class="k"&gt;type&lt;/span&gt; &lt;span class="n"&gt;BookHandler&lt;/span&gt; &lt;span class="k"&gt;struct&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;service&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;application&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;BookService&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="c"&gt;// NewBookHandler is Ore's initializer - it resolves *BookService from the container.&lt;/span&gt;
&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="n"&gt;NewBookHandler&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;ctx&lt;/span&gt; &lt;span class="n"&gt;context&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Context&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;BookHandler&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;context&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Context&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;svc&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;ctx&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Get&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;application&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;BookService&lt;/span&gt;&lt;span class="p"&gt;](&lt;/span&gt;&lt;span class="n"&gt;ctx&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;BookHandler&lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;&lt;span class="n"&gt;service&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt; &lt;span class="n"&gt;svc&lt;/span&gt;&lt;span class="p"&gt;},&lt;/span&gt; &lt;span class="n"&gt;ctx&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;h&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;BookHandler&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="n"&gt;CreateBook&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt; &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ResponseWriter&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;r&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Request&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="k"&gt;var&lt;/span&gt; &lt;span class="n"&gt;input&lt;/span&gt; &lt;span class="k"&gt;struct&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="n"&gt;Title&lt;/span&gt;  &lt;span class="kt"&gt;string&lt;/span&gt; &lt;span class="s"&gt;`json:"title"`&lt;/span&gt;
        &lt;span class="n"&gt;Author&lt;/span&gt; &lt;span class="kt"&gt;string&lt;/span&gt; &lt;span class="s"&gt;`json:"author"`&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;
    &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;json&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;NewDecoder&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;r&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Body&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Decode&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;input&lt;/span&gt;&lt;span class="p"&gt;);&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Error&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="s"&gt;"invalid JSON body"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;StatusBadRequest&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
        &lt;span class="k"&gt;return&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;

    &lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;h&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;service&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;CreateBook&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;input&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Title&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;input&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Author&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;errors&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Is&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;err&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ErrInvalidBook&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
            &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Error&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Error&lt;/span&gt;&lt;span class="p"&gt;(),&lt;/span&gt; &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;StatusBadRequest&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
            &lt;span class="k"&gt;return&lt;/span&gt;
        &lt;span class="p"&gt;}&lt;/span&gt;
        &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Error&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="s"&gt;"something went wrong"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;StatusInternalServerError&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
        &lt;span class="k"&gt;return&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;

    &lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Header&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Set&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"Content-Type"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="s"&gt;"application/json"&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WriteHeader&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;StatusCreated&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="n"&gt;json&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;NewEncoder&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Encode&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;h&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;BookHandler&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="n"&gt;GetBook&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt; &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ResponseWriter&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;r&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Request&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;idStr&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;r&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;PathValue&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"id"&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="n"&gt;id&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;strconv&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ParseInt&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;idStr&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="m"&gt;10&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="m"&gt;64&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Error&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="s"&gt;"invalid id"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;StatusBadRequest&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
        &lt;span class="k"&gt;return&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;

    &lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;h&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;service&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;GetBook&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;id&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;errors&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Is&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;err&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ErrBookNotFound&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
            &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Error&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="s"&gt;"book not found"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;StatusNotFound&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
            &lt;span class="k"&gt;return&lt;/span&gt;
        &lt;span class="p"&gt;}&lt;/span&gt;
        &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Error&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="s"&gt;"something went wrong"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;StatusInternalServerError&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
        &lt;span class="k"&gt;return&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;

    &lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Header&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Set&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"Content-Type"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="s"&gt;"application/json"&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="n"&gt;json&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;NewEncoder&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Encode&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;h&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;BookHandler&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="n"&gt;ListBooks&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt; &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ResponseWriter&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;r&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Request&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;books&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;h&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;service&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ListBooks&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;
    &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Error&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="s"&gt;"something went wrong"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;StatusInternalServerError&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
        &lt;span class="k"&gt;return&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;

    &lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Header&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Set&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"Content-Type"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="s"&gt;"application/json"&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="n"&gt;json&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;NewEncoder&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Encode&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;books&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="c"&gt;// RegisterRoutes wires each route to the handler.&lt;/span&gt;
&lt;span class="c"&gt;// The handler itself is resolved fresh per request via r.Context() -&lt;/span&gt;
&lt;span class="c"&gt;// this means BookHandler and BookService are Scoped to each HTTP request.&lt;/span&gt;
&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="n"&gt;RegisterRoutes&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;mux&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ServeMux&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;mux&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;HandleFunc&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"POST /books"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="k"&gt;func&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt; &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ResponseWriter&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;r&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Request&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="n"&gt;handler&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;_&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Get&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;BookHandler&lt;/span&gt;&lt;span class="p"&gt;](&lt;/span&gt;&lt;span class="n"&gt;r&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Context&lt;/span&gt;&lt;span class="p"&gt;())&lt;/span&gt;
        &lt;span class="n"&gt;handler&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;CreateBook&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;r&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="p"&gt;})&lt;/span&gt;
    &lt;span class="n"&gt;mux&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;HandleFunc&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"GET /books/{id}"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="k"&gt;func&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt; &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ResponseWriter&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;r&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Request&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="n"&gt;handler&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;_&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Get&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;BookHandler&lt;/span&gt;&lt;span class="p"&gt;](&lt;/span&gt;&lt;span class="n"&gt;r&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Context&lt;/span&gt;&lt;span class="p"&gt;())&lt;/span&gt;
        &lt;span class="n"&gt;handler&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;GetBook&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;r&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="p"&gt;})&lt;/span&gt;
    &lt;span class="n"&gt;mux&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;HandleFunc&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"GET /books"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="k"&gt;func&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt; &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ResponseWriter&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;r&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Request&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="n"&gt;handler&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;_&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Get&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;BookHandler&lt;/span&gt;&lt;span class="p"&gt;](&lt;/span&gt;&lt;span class="n"&gt;r&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Context&lt;/span&gt;&lt;span class="p"&gt;())&lt;/span&gt;
        &lt;span class="n"&gt;handler&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ListBooks&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;w&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;r&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="p"&gt;})&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;p&gt;The route closures each call &lt;code&gt;ore.Get[*BookHandler](r.Context())&lt;/code&gt;. This is the scoping magic at work - Ore uses &lt;code&gt;r.Context()&lt;/code&gt; as the scope boundary. Every concurrent request gets its own &lt;code&gt;BookHandler&lt;/code&gt; and its own &lt;code&gt;BookService&lt;/code&gt;, completely isolated. The shared singleton &lt;code&gt;*DB&lt;/code&gt; underneath is reused across all of them.&lt;/p&gt;




&lt;h2&gt;
  
  
  💉 Step 6: The DI Container - The Composition Root
&lt;/h2&gt;

&lt;p&gt;This is the most important wiring file in the whole project. &lt;code&gt;di/container.go&lt;/code&gt; is the &lt;strong&gt;only&lt;/strong&gt; place that imports all layers simultaneously. It's where you make the concrete choices: "use SQLite, not Postgres", "use this service, not a mock."&lt;br&gt;
&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="c"&gt;// di/container.go&lt;/span&gt;
&lt;span class="k"&gt;package&lt;/span&gt; &lt;span class="n"&gt;di&lt;/span&gt;

&lt;span class="k"&gt;import&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;
    &lt;span class="s"&gt;"booklib/application"&lt;/span&gt;
    &lt;span class="s"&gt;"booklib/domain"&lt;/span&gt;
    &lt;span class="s"&gt;"booklib/infrastructure"&lt;/span&gt;
    &lt;span class="s"&gt;"booklib/presentation"&lt;/span&gt;

    &lt;span class="s"&gt;"github.com/firasdarwish/ore"&lt;/span&gt;
&lt;span class="p"&gt;)&lt;/span&gt;

&lt;span class="c"&gt;// Register wires the entire application dependency graph into Ore.&lt;/span&gt;
&lt;span class="c"&gt;// This is the composition root - the one place that sees all layers.&lt;/span&gt;
&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="n"&gt;Register&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="c"&gt;// 🗄️ Register the SQLite DB as a Singleton.&lt;/span&gt;
    &lt;span class="c"&gt;// One *DB instance for the whole application lifetime.&lt;/span&gt;
    &lt;span class="c"&gt;// NewDB opens the connection and runs migrations on first resolution.&lt;/span&gt;
    &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;RegisterFunc&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;infrastructure&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;DB&lt;/span&gt;&lt;span class="p"&gt;](&lt;/span&gt;
        &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Singleton&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
        &lt;span class="n"&gt;infrastructure&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;NewDB&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
    &lt;span class="p"&gt;)&lt;/span&gt;

    &lt;span class="c"&gt;// 📦 Register the SQLite repository as a Singleton.&lt;/span&gt;
    &lt;span class="c"&gt;// It depends on *DB, which Ore resolves above.&lt;/span&gt;
    &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;RegisterFunc&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;infrastructure&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;SQLiteBookRepository&lt;/span&gt;&lt;span class="p"&gt;](&lt;/span&gt;
        &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Singleton&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
        &lt;span class="n"&gt;infrastructure&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;NewSQLiteBookRepository&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
    &lt;span class="p"&gt;)&lt;/span&gt;

    &lt;span class="c"&gt;// 🔗 Alias: whenever someone asks for domain.BookRepository (the interface),&lt;/span&gt;
    &lt;span class="c"&gt;// Ore hands them *infrastructure.SQLiteBookRepository (the implementation).&lt;/span&gt;
    &lt;span class="c"&gt;// This is dependency inversion - the application layer never knows SQLite exists.&lt;/span&gt;
    &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;RegisterAlias&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;BookRepository&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;infrastructure&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;SQLiteBookRepository&lt;/span&gt;&lt;span class="p"&gt;]()&lt;/span&gt;

    &lt;span class="c"&gt;// ⚡ Register BookService as Scoped - a fresh instance per request context.&lt;/span&gt;
    &lt;span class="c"&gt;// It depends on domain.BookRepository, resolved via the alias above.&lt;/span&gt;
    &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;RegisterFunc&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;application&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;BookService&lt;/span&gt;&lt;span class="p"&gt;](&lt;/span&gt;
        &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Scoped&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
        &lt;span class="n"&gt;application&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;NewBookService&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
    &lt;span class="p"&gt;)&lt;/span&gt;

    &lt;span class="c"&gt;// 🌐 Register BookHandler as Scoped - a fresh instance per request context.&lt;/span&gt;
    &lt;span class="c"&gt;// It depends on *application.BookService.&lt;/span&gt;
    &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;RegisterFunc&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;presentation&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;BookHandler&lt;/span&gt;&lt;span class="p"&gt;](&lt;/span&gt;
        &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Scoped&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
        &lt;span class="n"&gt;presentation&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;NewBookHandler&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
    &lt;span class="p"&gt;)&lt;/span&gt;

    &lt;span class="c"&gt;// 🔒 Seal the container - no new registrations allowed after this point.&lt;/span&gt;
    &lt;span class="c"&gt;// Any attempt to register after Seal() will panic immediately,&lt;/span&gt;
    &lt;span class="c"&gt;// preventing accidental runtime mutation of the dependency graph.&lt;/span&gt;
    &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Seal&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;

    &lt;span class="c"&gt;// ✅ Validate the full dependency graph at startup.&lt;/span&gt;
    &lt;span class="c"&gt;// Ore will catch:&lt;/span&gt;
    &lt;span class="c"&gt;//   - Missing dependencies&lt;/span&gt;
    &lt;span class="c"&gt;//   - Circular dependencies&lt;/span&gt;
    &lt;span class="c"&gt;//   - Lifetime misalignments (e.g. a Singleton depending on a Scoped)&lt;/span&gt;
    &lt;span class="c"&gt;// Better to crash loudly on startup than silently misbehave at 3am. 🔥&lt;/span&gt;
    &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Validate&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;

    &lt;span class="c"&gt;// ⚡ Disable per-call validation now that we've verified everything.&lt;/span&gt;
    &lt;span class="c"&gt;// Ore validates on every Get() call by default - useful in development,&lt;/span&gt;
    &lt;span class="c"&gt;// but unnecessary overhead once Validate() has blessed the graph.&lt;/span&gt;
    &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;DisableValidation&lt;/span&gt; &lt;span class="o"&gt;=&lt;/span&gt; &lt;span class="no"&gt;true&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;p&gt;The &lt;code&gt;RegisterAlias&lt;/code&gt; line is the crux of Clean Architecture in code form. &lt;code&gt;BookService&lt;/code&gt; calls &lt;code&gt;ore.Get[domain.BookRepository](ctx)&lt;/code&gt; - asking for an interface. The alias tells Ore: "that interface? Give them &lt;code&gt;*SQLiteBookRepository&lt;/code&gt;." If tomorrow you want to swap to Postgres, you change two lines in this file and nothing else in the project changes.&lt;/p&gt;




&lt;h2&gt;
  
  
  🚀 Step 7: main.go - Startup, Routes, and Goodbye
&lt;/h2&gt;



&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="c"&gt;// main.go&lt;/span&gt;
&lt;span class="k"&gt;package&lt;/span&gt; &lt;span class="n"&gt;main&lt;/span&gt;

&lt;span class="k"&gt;import&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;
    &lt;span class="s"&gt;"booklib/di"&lt;/span&gt;
    &lt;span class="s"&gt;"booklib/presentation"&lt;/span&gt;
    &lt;span class="s"&gt;"context"&lt;/span&gt;
    &lt;span class="s"&gt;"log"&lt;/span&gt;
    &lt;span class="s"&gt;"net/http"&lt;/span&gt;
    &lt;span class="s"&gt;"os"&lt;/span&gt;
    &lt;span class="s"&gt;"os/signal"&lt;/span&gt;
    &lt;span class="s"&gt;"syscall"&lt;/span&gt;
    &lt;span class="s"&gt;"time"&lt;/span&gt;

    &lt;span class="s"&gt;"github.com/firasdarwish/ore"&lt;/span&gt;
&lt;span class="p"&gt;)&lt;/span&gt;

&lt;span class="c"&gt;// Shutdowner is our graceful-shutdown interface.&lt;/span&gt;
&lt;span class="c"&gt;// Any singleton that implements Shutdown() will be discovered automatically by Ore.&lt;/span&gt;
&lt;span class="c"&gt;// We define it here in main - Ore doesn't care where it's defined,&lt;/span&gt;
&lt;span class="c"&gt;// only that the type matches at runtime.&lt;/span&gt;
&lt;span class="k"&gt;type&lt;/span&gt; &lt;span class="n"&gt;Shutdowner&lt;/span&gt; &lt;span class="k"&gt;interface&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;Shutdown&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;

&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="n"&gt;main&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="n"&gt;log&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Println&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"📚 BookLib starting up..."&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;

    &lt;span class="c"&gt;// Wire up everything - this is the only line in main that cares about DI&lt;/span&gt;
    &lt;span class="n"&gt;di&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Register&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;

    &lt;span class="c"&gt;// Set up routes&lt;/span&gt;
    &lt;span class="n"&gt;mux&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;NewServeMux&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;
    &lt;span class="n"&gt;presentation&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;RegisterRoutes&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;mux&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;

    &lt;span class="n"&gt;server&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Server&lt;/span&gt;&lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="n"&gt;Addr&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;         &lt;span class="s"&gt;":8080"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
        &lt;span class="n"&gt;Handler&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;      &lt;span class="n"&gt;mux&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
        &lt;span class="n"&gt;ReadTimeout&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt;  &lt;span class="m"&gt;10&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt; &lt;span class="n"&gt;time&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Second&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
        &lt;span class="n"&gt;WriteTimeout&lt;/span&gt;&lt;span class="o"&gt;:&lt;/span&gt; &lt;span class="m"&gt;10&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt; &lt;span class="n"&gt;time&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Second&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;

    &lt;span class="c"&gt;// Start serving in a goroutine so we can listen for shutdown signals below&lt;/span&gt;
    &lt;span class="k"&gt;go&lt;/span&gt; &lt;span class="k"&gt;func&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="n"&gt;log&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Println&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"🌍 Server listening on http://localhost:8080"&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
        &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;server&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ListenAndServe&lt;/span&gt;&lt;span class="p"&gt;();&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="o"&gt;&amp;amp;&amp;amp;&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="n"&gt;http&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;ErrServerClosed&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
            &lt;span class="n"&gt;log&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Fatalf&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"❌ server crashed: %v"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
        &lt;span class="p"&gt;}&lt;/span&gt;
    &lt;span class="p"&gt;}()&lt;/span&gt;

    &lt;span class="c"&gt;// Block until we receive SIGINT or SIGTERM (Ctrl+C or `kill`)&lt;/span&gt;
    &lt;span class="n"&gt;quit&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="nb"&gt;make&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="k"&gt;chan&lt;/span&gt; &lt;span class="n"&gt;os&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Signal&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="m"&gt;1&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="n"&gt;signal&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Notify&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;quit&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;syscall&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;SIGINT&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;syscall&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;SIGTERM&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="o"&gt;&amp;lt;-&lt;/span&gt;&lt;span class="n"&gt;quit&lt;/span&gt;

    &lt;span class="n"&gt;log&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Println&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"👋 Shutdown signal received - draining requests..."&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;

    &lt;span class="c"&gt;// Give in-flight requests 5 seconds to finish&lt;/span&gt;
    &lt;span class="n"&gt;ctx&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;cancel&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;context&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;WithTimeout&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;context&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Background&lt;/span&gt;&lt;span class="p"&gt;(),&lt;/span&gt; &lt;span class="m"&gt;5&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;time&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Second&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="k"&gt;defer&lt;/span&gt; &lt;span class="n"&gt;cancel&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;
    &lt;span class="k"&gt;if&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;server&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Shutdown&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;ctx&lt;/span&gt;&lt;span class="p"&gt;);&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;!=&lt;/span&gt; &lt;span class="no"&gt;nil&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="n"&gt;log&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Printf&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"⚠️  HTTP shutdown error: %v"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;

    &lt;span class="c"&gt;// 🔑 Graceful service cleanup via Ore.&lt;/span&gt;
    &lt;span class="c"&gt;// GetResolvedSingletons finds every resolved singleton that implements Shutdowner.&lt;/span&gt;
    &lt;span class="c"&gt;// Crucially, Ore returns them in REVERSE dependency order -&lt;/span&gt;
    &lt;span class="c"&gt;// so the DB is closed AFTER any services that depend on it.&lt;/span&gt;
    &lt;span class="c"&gt;// No manual enumeration. No forgetting a service. Ore handles it. 💪&lt;/span&gt;
    &lt;span class="n"&gt;log&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Println&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"🧹 Cleaning up singletons..."&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="n"&gt;shutdownables&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;GetResolvedSingletons&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="n"&gt;Shutdowner&lt;/span&gt;&lt;span class="p"&gt;]()&lt;/span&gt;
    &lt;span class="k"&gt;for&lt;/span&gt; &lt;span class="n"&gt;_&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;s&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="k"&gt;range&lt;/span&gt; &lt;span class="n"&gt;shutdownables&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
        &lt;span class="n"&gt;s&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Shutdown&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;
    &lt;span class="p"&gt;}&lt;/span&gt;

    &lt;span class="n"&gt;log&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Println&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"✅ Clean exit. Goodbye!"&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;p&gt;The shutdown sequence is worth reading twice. We don't call &lt;code&gt;db.Close()&lt;/code&gt; explicitly anywhere in &lt;code&gt;main.go&lt;/code&gt;. We don't maintain a list of "things to clean up." We just ask Ore: "give me every resolved singleton that can shut itself down, in dependency order." Ore knows the graph - it knows &lt;code&gt;*DB&lt;/code&gt; was resolved as a dependency of &lt;code&gt;*SQLiteBookRepository&lt;/code&gt;, so &lt;code&gt;*DB.Shutdown()&lt;/code&gt; runs after &lt;code&gt;SQLiteBookRepository&lt;/code&gt; is done. As you add more singletons (caches, queue publishers, audit log flushers), they just need to implement &lt;code&gt;Shutdown()&lt;/code&gt; and Ore includes them automatically.&lt;/p&gt;




&lt;h2&gt;
  
  
  🧪 Let's Take It for a Spin
&lt;/h2&gt;



&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight shell"&gt;&lt;code&gt;go run main.go
&lt;span class="c"&gt;# 📚 BookLib starting up...&lt;/span&gt;
&lt;span class="c"&gt;# ✅ SQLite connected and schema ready&lt;/span&gt;
&lt;span class="c"&gt;# 🌍 Server listening on http://localhost:8080&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;p&gt;In another terminal:&lt;br&gt;
&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight shell"&gt;&lt;code&gt;&lt;span class="c"&gt;# ➕ Create a few books&lt;/span&gt;
curl &lt;span class="nt"&gt;-s&lt;/span&gt; &lt;span class="nt"&gt;-X&lt;/span&gt; POST http://localhost:8080/books &lt;span class="se"&gt;\&lt;/span&gt;
  &lt;span class="nt"&gt;-H&lt;/span&gt; &lt;span class="s2"&gt;"Content-Type: application/json"&lt;/span&gt; &lt;span class="se"&gt;\&lt;/span&gt;
  &lt;span class="nt"&gt;-d&lt;/span&gt; &lt;span class="s1"&gt;'{"title":"The Go Programming Language","author":"Donovan &amp;amp; Kernighan"}'&lt;/span&gt; | jq

&lt;span class="c"&gt;# {&lt;/span&gt;
&lt;span class="c"&gt;#   "ID": 1,&lt;/span&gt;
&lt;span class="c"&gt;#   "Title": "The Go Programming Language",&lt;/span&gt;
&lt;span class="c"&gt;#   "Author": "Donovan &amp;amp; Kernighan"&lt;/span&gt;
&lt;span class="c"&gt;# }&lt;/span&gt;

curl &lt;span class="nt"&gt;-s&lt;/span&gt; &lt;span class="nt"&gt;-X&lt;/span&gt; POST http://localhost:8080/books &lt;span class="se"&gt;\&lt;/span&gt;
  &lt;span class="nt"&gt;-H&lt;/span&gt; &lt;span class="s2"&gt;"Content-Type: application/json"&lt;/span&gt; &lt;span class="se"&gt;\&lt;/span&gt;
  &lt;span class="nt"&gt;-d&lt;/span&gt; &lt;span class="s1"&gt;'{"title":"Clean Architecture","author":"Robert C. Martin"}'&lt;/span&gt; | jq

&lt;span class="c"&gt;# 📚 List all books&lt;/span&gt;
curl &lt;span class="nt"&gt;-s&lt;/span&gt; http://localhost:8080/books | jq

&lt;span class="c"&gt;# 🔍 Get a specific book&lt;/span&gt;
curl &lt;span class="nt"&gt;-s&lt;/span&gt; http://localhost:8080/books/1 | jq

&lt;span class="c"&gt;# ❌ Try a bad request&lt;/span&gt;
curl &lt;span class="nt"&gt;-s&lt;/span&gt; &lt;span class="nt"&gt;-X&lt;/span&gt; POST http://localhost:8080/books &lt;span class="se"&gt;\&lt;/span&gt;
  &lt;span class="nt"&gt;-H&lt;/span&gt; &lt;span class="s2"&gt;"Content-Type: application/json"&lt;/span&gt; &lt;span class="se"&gt;\&lt;/span&gt;
  &lt;span class="nt"&gt;-d&lt;/span&gt; &lt;span class="s1"&gt;'{"title":""}'&lt;/span&gt; | jq
&lt;span class="c"&gt;# book title and author are required&lt;/span&gt;

&lt;span class="c"&gt;# Press Ctrl+C:&lt;/span&gt;
&lt;span class="c"&gt;# 👋 Shutdown signal received - draining requests...&lt;/span&gt;
&lt;span class="c"&gt;# 🧹 Cleaning up singletons...&lt;/span&gt;
&lt;span class="c"&gt;# 🔌 Closing SQLite connection...&lt;/span&gt;
&lt;span class="c"&gt;# ✅ Clean exit. Goodbye!&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;p&gt;Restart the server and the books are still there - they're in &lt;code&gt;books.db&lt;/code&gt;, a real SQLite file on disk.&lt;/p&gt;




&lt;h2&gt;
  
  
  🔬 How Ore Sees the Dependency Graph
&lt;/h2&gt;

&lt;p&gt;Here's what happens under the hood when a &lt;code&gt;GET /books/1&lt;/code&gt; request comes in:&lt;br&gt;
&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight plaintext"&gt;&lt;code&gt;r.Context()
    │
    ▼  ore.Get[*BookHandler](r.Context())
┌──────────────────────────────────┐
│  [Scoped] *BookHandler           │  ← fresh per request
│    depends on ↓                  │
│  [Scoped] *BookService           │  ← fresh per request
│    depends on ↓                  │
│  [Alias]  domain.BookRepository  │  ← resolves to ↓
│  [Singleton] *SQLiteBookRepo     │  ← shared across all requests
│    depends on ↓                  │
│  [Singleton] *DB                 │  ← one connection pool, always
└──────────────────────────────────┘
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;p&gt;The two singletons at the bottom are created once, ever. The scoped services are created fresh for each request and garbage collected when the request context ends. Ore manages all of this from the registrations in &lt;code&gt;di/container.go&lt;/code&gt;. You never call &lt;code&gt;new()&lt;/code&gt; manually for any of these types.&lt;/p&gt;




&lt;h2&gt;
  
  
  🔄 The Payoff: Swapping SQLite for Postgres
&lt;/h2&gt;

&lt;p&gt;Remember when we said this architecture makes swapping databases a two-line change? Here's the proof. Add a &lt;code&gt;PostgresBookRepository&lt;/code&gt; to infrastructure, then in &lt;code&gt;di/container.go&lt;/code&gt;:&lt;br&gt;
&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="c"&gt;// Before (SQLite):&lt;/span&gt;
&lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;RegisterFunc&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;infrastructure&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;SQLiteBookRepository&lt;/span&gt;&lt;span class="p"&gt;](&lt;/span&gt;&lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Singleton&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;infrastructure&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;NewSQLiteBookRepository&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
&lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;RegisterAlias&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;BookRepository&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;infrastructure&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;SQLiteBookRepository&lt;/span&gt;&lt;span class="p"&gt;]()&lt;/span&gt;

&lt;span class="c"&gt;// After (Postgres):&lt;/span&gt;
&lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;RegisterFunc&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;infrastructure&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;PostgresBookRepository&lt;/span&gt;&lt;span class="p"&gt;](&lt;/span&gt;&lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Singleton&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;infrastructure&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;NewPostgresBookRepository&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
&lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;RegisterAlias&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;BookRepository&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;infrastructure&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;PostgresBookRepository&lt;/span&gt;&lt;span class="p"&gt;]()&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;p&gt;&lt;code&gt;BookService&lt;/code&gt;, &lt;code&gt;BookHandler&lt;/code&gt;, your tests, your domain rules - none of them change. Not a single line. That's the whole point. 🎯&lt;/p&gt;




&lt;h2&gt;
  
  
  🧪 Testing with Isolated Containers
&lt;/h2&gt;

&lt;p&gt;One of Ore's killer features for testing is &lt;code&gt;ore.NewContainer()&lt;/code&gt;. Each test gets its own isolated dependency graph - no shared state, no flaky tests, no "it passes locally but fails in CI" mysteries.&lt;br&gt;
&lt;/p&gt;

&lt;div class="highlight js-code-highlight"&gt;
&lt;pre class="highlight go"&gt;&lt;code&gt;&lt;span class="k"&gt;func&lt;/span&gt; &lt;span class="n"&gt;TestCreateBook&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;t&lt;/span&gt; &lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;testing&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;T&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
    &lt;span class="c"&gt;// 🧱 Build a fresh, isolated container just for this test&lt;/span&gt;
    &lt;span class="n"&gt;container&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;NewContainer&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;

    &lt;span class="c"&gt;// Register a mock repo instead of the real SQLite one&lt;/span&gt;
    &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;RegisterFuncToContainer&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;BookRepository&lt;/span&gt;&lt;span class="p"&gt;](&lt;/span&gt;&lt;span class="n"&gt;container&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Scoped&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
        &lt;span class="k"&gt;func&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;ctx&lt;/span&gt; &lt;span class="n"&gt;context&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Context&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;domain&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;BookRepository&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;context&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Context&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt; &lt;span class="p"&gt;{&lt;/span&gt;
            &lt;span class="k"&gt;return&lt;/span&gt; &lt;span class="o"&gt;&amp;amp;&lt;/span&gt;&lt;span class="n"&gt;MockBookRepository&lt;/span&gt;&lt;span class="p"&gt;{},&lt;/span&gt; &lt;span class="n"&gt;ctx&lt;/span&gt;
        &lt;span class="p"&gt;},&lt;/span&gt;
    &lt;span class="p"&gt;)&lt;/span&gt;

    &lt;span class="c"&gt;// Wire up BookService - same initializer as production&lt;/span&gt;
    &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;RegisterFuncToContainer&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;application&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;BookService&lt;/span&gt;&lt;span class="p"&gt;](&lt;/span&gt;&lt;span class="n"&gt;container&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Scoped&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
        &lt;span class="n"&gt;application&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;NewBookService&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt;
    &lt;span class="p"&gt;)&lt;/span&gt;

    &lt;span class="n"&gt;ctx&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;context&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Background&lt;/span&gt;&lt;span class="p"&gt;()&lt;/span&gt;
    &lt;span class="n"&gt;svc&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;_&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;ore&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;GetFromContainer&lt;/span&gt;&lt;span class="p"&gt;[&lt;/span&gt;&lt;span class="o"&gt;*&lt;/span&gt;&lt;span class="n"&gt;application&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;BookService&lt;/span&gt;&lt;span class="p"&gt;](&lt;/span&gt;&lt;span class="n"&gt;container&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;ctx&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;

    &lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt; &lt;span class="o"&gt;:=&lt;/span&gt; &lt;span class="n"&gt;svc&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;CreateBook&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="s"&gt;"Clean Code"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="s"&gt;"Robert Martin"&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;

    &lt;span class="n"&gt;assert&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;NoError&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;t&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;err&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="n"&gt;assert&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Equal&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;t&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="s"&gt;"Clean Code"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Title&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
    &lt;span class="n"&gt;assert&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Equal&lt;/span&gt;&lt;span class="p"&gt;(&lt;/span&gt;&lt;span class="n"&gt;t&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="s"&gt;"Robert Martin"&lt;/span&gt;&lt;span class="p"&gt;,&lt;/span&gt; &lt;span class="n"&gt;book&lt;/span&gt;&lt;span class="o"&gt;.&lt;/span&gt;&lt;span class="n"&gt;Author&lt;/span&gt;&lt;span class="p"&gt;)&lt;/span&gt;
&lt;span class="p"&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;

&lt;/div&gt;



&lt;p&gt;The mock repo satisfies &lt;code&gt;domain.BookRepository&lt;/code&gt;. &lt;code&gt;BookService&lt;/code&gt; doesn't know or care. The test runs fast with zero disk I/O. 🚀&lt;/p&gt;




&lt;h2&gt;
  
  
  💡 Ore Patterns You'll Use Again and Again
&lt;/h2&gt;

&lt;p&gt;By building this app, you've touched the core toolkit:&lt;/p&gt;

&lt;p&gt;&lt;code&gt;RegisterFunc&lt;/code&gt; with &lt;code&gt;ore.Singleton&lt;/code&gt; - for anything expensive to create and safe to share: DB connections, HTTP clients, config structs.&lt;/p&gt;

&lt;p&gt;&lt;code&gt;RegisterFunc&lt;/code&gt; with &lt;code&gt;ore.Scoped&lt;/code&gt; - for anything that should be isolated per request: services, handlers, transaction managers.&lt;/p&gt;

&lt;p&gt;&lt;code&gt;RegisterAlias&lt;/code&gt; - the dependency inversion trick. Register a concrete, alias an interface to it. Every caller gets the interface; Ore handles the mapping.&lt;/p&gt;

&lt;p&gt;&lt;code&gt;ore.Seal()&lt;/code&gt; + &lt;code&gt;ore.Validate()&lt;/code&gt; - your safety net. Call them both at startup. Catch misconfigured graphs before the first request, not during a production incident.&lt;/p&gt;

&lt;p&gt;&lt;code&gt;ore.GetResolvedSingletons[T]()&lt;/code&gt; - the graceful shutdown pattern. Define a cleanup interface, let your services implement it, and Ore gives you a sorted list at exit time. No maintenance required as the app grows.&lt;/p&gt;




&lt;h2&gt;
  
  
  🏁 Wrapping Up
&lt;/h2&gt;

&lt;p&gt;Here's what we built and why it matters:&lt;/p&gt;

&lt;p&gt;&lt;strong&gt;The domain layer&lt;/strong&gt; has zero external dependencies. Your business rules could be tested in a brand new Go project with just the standard library. That's power.&lt;/p&gt;

&lt;p&gt;&lt;strong&gt;The application layer&lt;/strong&gt; depends only on domain interfaces. It doesn't know if it's talking to SQLite, Postgres, a mock, or a remote API. It just does its job.&lt;/p&gt;

&lt;p&gt;&lt;strong&gt;The infrastructure layer&lt;/strong&gt; does the dirty work - SQL queries, connection management, schema migrations - and implements exactly the interface the domain asked for.&lt;/p&gt;

&lt;p&gt;&lt;strong&gt;The presentation layer&lt;/strong&gt; translates HTTP to application calls and back. If you add gRPC next month, it's just a new presentation file.&lt;/p&gt;

&lt;p&gt;&lt;strong&gt;The DI container&lt;/strong&gt; is the only place that sees the whole picture. Changing the database is two lines. Swapping to a mock in tests is five lines. The rest of the project never notices. 😌&lt;/p&gt;

&lt;p&gt;Clean Architecture and Ore are a natural match. Ore makes the composition root explicit, validated, and lifecycle-aware. Clean Architecture gives every piece of your app a clear home and clear rules for how it can talk to its neighbors.&lt;/p&gt;

&lt;p&gt;Now go build something real. 🚀&lt;/p&gt;




&lt;p&gt;&lt;em&gt;Full Ore documentation: &lt;a href="https://ore.lilury.com" rel="noopener noreferrer"&gt;ore.lilury.com&lt;/a&gt; - source on &lt;a href="https://github.com/firasdarwish/ore" rel="noopener noreferrer"&gt;GitHub&lt;/a&gt;&lt;/em&gt;&lt;/p&gt;

</description>
      <category>go</category>
      <category>ore</category>
      <category>di</category>
      <category>architecture</category>
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