Load environment variables dynamically in Go.

$ go get github.com/subosito/gotenv

Store your configuration to .env file on your root directory of your project:

APP_ID=1234567
APP_SECRET=abcdef

You may also add export in front of each line so you can source the file in bash:

export APP_ID=1234567
export APP_SECRET=abcdef

Put the gotenv package on your import statement:

import "github.com/subosito/gotenv"

Then somewhere on your application code, put:

gotenv.Load()

Behind the scene it will then load .env file and export the valid variables to the environment variables. Make sure you call the method as soon as possible to ensure all variables are loaded, say, put it on init() function.

Once loaded you can use os.Getenv() to get the value of the variable.

Here's the final example:

package main

import (
	"github.com/subosito/gotenv"
	"log"
	"os"
)

func init() {
	gotenv.Load()
}

func main() {
	log.Println(os.Getenv("APP_ID"))     // "1234567"
	log.Println(os.Getenv("APP_SECRET")) // "abcdef"
}

You can also load other than .env file if you wish. Just supply filenames when calling Load():

gotenv.Load(".env.production", "credentials")

That's it :)

Just in case you want to parse environment variables from any io.Reader, gotenv keeps its Parse() function as public API so you can utilize that.

// import "strings"

pairs := gotenv.Parse(strings.NewReader("FOO=test\nBAR=$FOO"))
// gotenv.Env{"FOO": "test", "BAR": "test"}

pairs = gotenv.Parse(strings.NewReader(`FOO="bar"`))
// gotenv.Env{"FOO": "bar"}

Parse ignores invalid lines and returns Env of valid environment variables.

The gotenv package is a Go port of dotenv project. Most logic and regexp pattern is taken from there and aims will be compatible as close as possible.