Initial part of #435
4 KiB
gotenv
Load environment variables dynamically in Go.
Usage
Put the gotenv package on your import
statement:
import "github.com/subosito/gotenv"
To modify your app environment variables, gotenv
expose 2 main functions:
gotenv.Load
gotenv.Apply
By default, gotenv.Load
will look for a file called .env
in the current working directory.
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 it loads all variables, say, put it on init()
function.
Once loaded you can use os.Getenv()
to get the value of the variable.
Let's say you have .env
file:
APP_ID=1234567
APP_SECRET=abcdef
Here's the example of your app:
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()
. It will load them in order and the first value set for a variable will win.:
gotenv.Load(".env.production", "credentials")
While gotenv.Load
loads entries from .env
file, gotenv.Apply
allows you to use any io.Reader
:
gotenv.Apply(strings.NewReader("APP_ID=1234567"))
log.Println(os.Getenv("APP_ID"))
// Output: "1234567"
Both gotenv.Load
and gotenv.Apply
DO NOT overrides existing environment variables. If you want to override existing ones, you can see section below.
Environment Overrides
Besides above functions, gotenv
also provides another functions that overrides existing:
gotenv.OverLoad
gotenv.OverApply
Here's the example of this overrides behavior:
os.Setenv("HELLO", "world")
// NOTE: using Apply existing value will be reserved
gotenv.Apply(strings.NewReader("HELLO=universe"))
fmt.Println(os.Getenv("HELLO"))
// Output: "world"
// NOTE: using OverApply existing value will be overridden
gotenv.OverApply(strings.NewReader("HELLO=universe"))
fmt.Println(os.Getenv("HELLO"))
// Output: "universe"
Throw a Panic
Both gotenv.Load
and gotenv.OverLoad
returns an error on something wrong occurred, like your env file is not exist, and so on. To make it easier to use, gotenv
also provides gotenv.Must
helper, to let it panic when an error returned.
err := gotenv.Load(".env-is-not-exist")
fmt.Println("error", err)
// error: open .env-is-not-exist: no such file or directory
gotenv.Must(gotenv.Load, ".env-is-not-exist")
// it will throw a panic
// panic: open .env-is-not-exist: no such file or directory
Another Scenario
Just in case you want to parse environment variables from any io.Reader
, gotenv keeps its Parse
and StrictParse
function as public API so you can use that.
// import "strings"
pairs := gotenv.Parse(strings.NewReader("FOO=test\nBAR=$FOO"))
// gotenv.Env{"FOO": "test", "BAR": "test"}
err, pairs = gotenv.StrictParse(strings.NewReader(`FOO="bar"`))
// gotenv.Env{"FOO": "bar"}
Parse
ignores invalid lines and returns Env
of valid environment variables, while StrictParse
returns an error for invalid lines.
Notes
The gotenv package is a Go port of dotenv
project with some additions made for Go. For general features, it aims to be compatible as close as possible.