A Go port of Ruby's dotenv library (Loads environment variables from `.env`.)
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joho Merge pull request #60 from coolaj86/precedence
explicitly state env precedence and convention
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README.md

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A Go (golang) port of the Ruby dotenv project (which loads env vars from a .env file)

From the original Library:

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 (for loading in env for your own daemons etc) or as a bin command.

There is test coverage and CI for both linuxish and windows environments, but I make no guarantees about the bin version working on windows.

Installation

As a library

go get github.com/joho/godotenv

or if you want to use it as a bin command

go get github.com/joho/godotenv/cmd/godotenv

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 (
    "github.com/joho/godotenv"
    "log"
    "os"
)

func main() {
  err := godotenv.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
}

If you're even lazier than that, you can just take advantage of the autoload package which will read in .env on import

import _ "github.com/joho/godotenv/autoload"

While .env in the project root is the default, you don't have to be constrained, both examples below are 100% legit

_ = godotenv.Load("somerandomfile")
_ = godotenv.Load("filenumberone.env", "filenumbertwo.env")

If you want to be really fancy with your env file you can do comments and exports (below is a valid 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

as a final aside, if you don't want godotenv munging your env you can just get a map back instead

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

s3Bucket := myEnv["S3_BUCKET"]

... or from an io.Reader instead of a local file

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

... or from a string if you so desire

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

Precendence & Conventions

Existing envs take precendence of envs that are loaded later.

The convention for managing multiple environments (i.e. development, test, production) is to create an env named {YOURAPP}_ENV and load envs in this order:

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

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

If you need to, you can also use godotenv.Overload() to defy this convention and overwrite existing envs instead of only supplanting them. Use with caution.

Command Mode

Assuming you've installed the command as above and you've got $GOPATH/bin in your $PATH

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

If you don't specify -f it will fall back on the default of loading .env in PWD

Writing Env Files

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

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

... or to a string

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

Contributing

Contributions are most welcome! The parser itself is pretty stupidly naive and I wouldn't be surprised if it breaks with edge cases.

code changes without tests will not be accepted

  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Added some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request

Releases

Releases should follow Semver though the first couple of releases are v1 and v1.1.

Use annotated tags for all releases. Example git tag -a v1.2.1

CI

Linux: Build Status Windows: Build status

Who?

The original library dotenv was written by Brandon Keepers, and this port was done by John Barton based off the tests/fixtures in the original library.