env

Go library which loads environment variables from .env files.
Ruby project dotenv port.

Storing configuration in the environment is one of the tenets of a twelve-factor app. Anything that is likely to change between deployment environments–such as resource handles for databases or credentials for external services–should be extracted from the code into environment variables.

But it is not always practical to set environment variables on development machines or continuous integration servers where multiple projects are run. Dotenv load variables from a .env file into ENV when the environment is bootstrapped.

It can be used as a library (to load into env for your own daemons, etc.) or as a bin command.

Installation

As a library

go get github.com/pchchv/env

As a bin command

go >= 1.17

go install github.com/pchchv/env/cmd/env@latest

go < 1.17

go get github.com/pchchv/env/cmd/env

Usage

Add your application configuration to your .env file in the root of your project:

S3_BUCKET=YOURS3BUCKET
SECRET_KEY=YOURSECRETKEYGOESHERE

Then in your Go app you can do something like

package main

import (
    "log"
    "os"

    "github.com/pchchv/env"
)

func main() {
  err := env.Load()
  if err != nil {
    log.Fatal("Error loading .env file")
  }

  s3Bucket := os.Getenv("S3_BUCKET")
  secretKey := os.Getenv("SECRET_KEY")

  // now do something with s3 or whatever
}

Also, you can simply take advantage of the autoload package which will read .env when importing

import _ "github.com/pchchv/env/autoload"

Although .env in the root of the project is used by default, you should not be restricted, both of the following examples are 100% acceptable

env.Load("somerandomfile")
env.Load("filenumberone.env", "filenumbertwo.env")

If you want to be really fancy with your env file, you can make comments and export (below is the correct env file)

# I am a comment and that is OK
SOME_VAR=someval
FOO=BAR # comments at line end are OK too
export BAR=BAZ

Or finally you can do YAML(ish) style

FOO: bar
BAR: baz

If you don't want env to change your environment, you can just get the map back

var myEnv map[string]string
myEnv, err := env.Read()

s3Bucket := myEnv["S3_BUCKET"]

or from an io.Reader instead of a local file

reader := getRemoteFile()
myEnv, err := env.Parse(reader)

... or from a string if you so desire

content := getRemoteFileContent()
myEnv, err := env.Unmarshal(content)

Precedence & Conventions

Existing envs take precedence of envs that are loaded later.

convention for managing multiple environments (i.e. development, testing, production) is to create an environment named {YOURAPP}_ENV and load the environments in that order:

env := os.Getenv("FOO_ENV")
if "" == env {
  env = "development"
}

env.Load(".env." + env + ".local")
if "test" != env {
  env.Load(".env.local")
}
env.Load(".env." + env)
env.Load() // The Original .env

If necessary, you can also use env.Overload() to break this convention and overwrite existing envs instead of just replacing them. Use with caution.

Command Mode

Suppose you installed the command as above, and you have $GOPATH/bin in $PATH.

env -f /some/path/to/.env some_command with some args

If you do not specify -f, it will load .env into PWD by default.

By default it will not override existing environment variables; you can do this with the -o flag.

Writing Env Files

env can also write a map representing the environment to a correctly-formatted and escaped file

env, err := env.Unmarshal("KEY=value")
err := env.Write(env, "./.env")

or to a string

env, err := env.Unmarshal("KEY=value")
content, err := env.Marshal(env)