GoDotEnv 
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
as a tool dependency:
go >= 1.24
go get -tool github.com/joho/godotenv/cmd/godotenv
or if you want to use it as a bin command
go install github.com/joho/godotenv/cmd/godotenv@latest
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/joho/godotenv"
)
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)
Variable name compatibility
Ruby's dotenv only allows [A-Za-z0-9_.] in key names, while Node's dotenv also permits -. godotenv has matched the Node charset since v1.4.0, so keys like MY-VAR parse cleanly here and in Node but will error under Ruby's dotenv.
Precedence & Conventions
Existing envs take precedence 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() // The Original .env
godotenv.Load(".env." + env)
if "test" != env {
godotenv.Load(".env.local")
}
godotenv.Load(".env." + env + ".local")
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
By default, it won't override existing environment variables; you can do that with the -o flag.
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 welcome, but with some caveats.
This library has been declared feature complete (see #182 for background) and will not be accepting issues or pull requests adding new functionality or breaking the library API.
Contributions would be gladly accepted that:
- bring this library's parsing into closer compatibility with the mainline dotenv implementations, in particular Ruby's dotenv and Node.js' dotenv
- keep the library up to date with the go ecosystem (ie CI bumps, documentation changes, changes in the core libraries)
- bug fixes for use cases that pertain to the library's purpose of easing development of codebases deployed into twelve factor environments
code changes without tests and references to peer dotenv implementations will not be accepted
- Fork it
- Create your feature branch (
git checkout -b my-new-feature)
- Commit your changes (
git commit -am 'Added some feature')
- Push to the branch (
git push origin my-new-feature)
- 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
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.
它是 Ruby 的 dotenv 的 Go 版移植:一个库加命令行工具,在应用启动时把 .env 文件里的环境变量加载进你的进程环境。