Reading from Go's .Env

Preface

When you are just starting out with Go, it might be a bit overwhelming to grasp how the language works right away. As I was following this tutorial, to my surprise it logged all .env variables as undefined. It was not easy to then find a simple article covering how to properly read from an .env file in Go.

This is a super quick tutorial from someone who just learned it as well. Enjoy!

Code Example

Let's start by importing needed dependencies:

package main

import (
    // Needed for terminal printing, similar to "console.log" in Node.js
    "fmt"
    // Helpful for logging errors
    "log"
    // Needed for accessing .env file
    "os"
    // Needed for importing/loading .env file
    "github.com/joho/godotenv"
)

Then let's write a type structure, I used Human for simplicity's sake. Any human needs to have a name and a secret age. After all, isn't there a saying that it is inappropriate to ask people about their age?

I also simplified age to a string so that someone could be "20" or "twenty" years old.

type human struct {
    Name string
    Age  string
}

Now lets start writing our main.

func main() {
    // Creates a variable 'creds' in memory and assigns
    // it to an object with type 'human'
    creds := human{
        // Given that name is stored as "NAME_TOKEN=Jade" & age is
        // "AGE_SECRET_TOKEN=34", we now can ask Getenv to give us
        // the value of a token based on the provided key.
        Name: os.Getenv("NAME_TOKEN"),
        Age:  os.Getenv("AGE_SECRET_TOKEN"),
    }

    // Simply prints "Jade is 34 years old." to check
    // that we correctly read from the .env file
    fmt.Println(creds.Name + " is " + creds.Age + " years old.")

}

If you were following with me until this point, you'd probably realize that running go run [filename].go won't give much result. That is because right now we are trying to read from something we haven't imported yet! Let's fix this:

// Init is called right on top of main
func init() {
    // Loads the .env file using godotenv.
    // Throws an error is the file cannot be found.
    if err := godotenv.Load(); err != nil {
        log.Print("No .env file found")
    }
}

Here's what we have by putting all the little pieces together. Good luck,
and let me know if you need more clarification!

package main

import (
    "fmt"
    "log"
    "os"

    "github.com/joho/godotenv"
)

type human struct {
    Name string
    Age  string
}

func init() {
    if err := godotenv.Load(); err != nil {
        log.Print("No .env file found")
    }
}

func main() {
    creds := human{
        Name: os.Getenv("NAME_TOKEN"),
        Age:  os.Getenv("AGE_SECRET_TOKEN"),
    }

    fmt.Printf(creds.Name + " is " + creds.Age + " years old.")

}

The output

On a personal note

For the first time I didn't let perfectionism consume me when writing something! This article, if I can call it that way, was meant more as a way for me to store notes than anything else. So if you have any feedback on how to improve the above code, do let me know and I will fix it!

Comments

[Alex Suslov]

Variables maybe load in docker env

if err := godotenv.Load(); err != nil {
  log.Println("warning .env file load error", err)
}

[Alex Suslov]

Some more:

Micro service version from git

var version=""
func main(){
  log.Printf("Starting  %v \n", version)
}

Build

go build -ldflags "-X main.version=`git describe --abbrev=0`" main.go

[Alex Suslov]

Best way is replace os.Getenv("NAME_TOKEN") with GetPanic("NAME_TOKEN").

// https://github.com/alexsuslov/godotenv/blob/master/load.go
// GetPanic get variable or panic
func GetPanic(key string) string {
    v, _ := syscall.Getenv(key)
    if v == "" {
        panic(key)
    }
    return v
}

[Arturo Avilés]

Great tutorial! Thanks Kate!

[Eric Ahnell]

As someone who doesn't know Go much more than you do, and wants to learn, this helps!