Practical Go Programming

This article was originally published on bmf-tech.com.

Practical Go Programming has been finished, so I'm leaving my reading notes.

I've been working with Go for several years, but I found it very educational to realize things I didn't know or had forgotten.

Variable Names

• The suffix for variable names of the Error type that satisfy the Error interface should be Error
  • ex. NotImplementedError
• The prefix for variable names declared with errors.New should be Err
  • ex. ErrNotImplemented := errors.New("Not Implemented!")
• While abbreviations are preferred for variable names, descriptive variable names are desirable for variables used far from their declaration
• Actively use abbreviated forms for variables
  • If you want to explicitly specify the type, you can use var

Package Names

• Packages named internal are not exposed outside the module (≒ cannot be used from packages other than the package where internal is located and its sub-packages)
• Avoid duplication of package names and function names
  • ○http.Server ✕http.HTTPServer
  • ○zip.NewWriter ✕zip.NewZipWriter
• Folders named . and _ and testdata are excluded from compilation

Interface Names

• In standard packages, interfaces with only a single method sometimes have the suffix er
  • ex. io.Reader, fmt.Stringer

Constants

• const can only be used for immutable values determined at compile time
• Be careful of unintended constant value shifts with iota
  • If there is a possibility of adding constants other than at the end, define each constant individually instead of using iota
  • Avoid using iota for values that will be used not only by a single process but also by other processes
  • ex. Be careful with values returned to clients in HTTP server responses
• To convert iota integer values to strings in logs, golang.org/x/tools/cmd/stringer can be used
  • Useful when it's cumbersome to trace the meaning of integer values

Data Masking

• Can be achieved by extending with the Stringer and GoStringer interfaces

Structs

• Struct embedding ≠ inheritance
  • Inheritance is a relationship where the child depends on the parent, but struct embedding is a relationship where the parent loosely depends on the child (might be misleading..). Not Is-A, but Has-A.
  • Delegation, not inheritance.
• If you want to distinguish from zero values and omit empty fields in struct fields, use pointer types for the fields

Functions

• Places where log.Fatal and panic can be used
  • main function, init function, functions with the Must prefix, and other application initialization processes

Testing

• Detecting order dependencies
  • go test -shuffle=on shuffles the order of test execution