A simple golang tool to set flag via environment variables inspired by Go: Best Practices for Production Environments
- Set flag via environment variables.
- Auto mapping environment variables to flag. (e.g.
DATABASE_PORTto-database-port) - Customizable env - flag mapping support.
- Min length (default is 3) support in order to avoid parsing short flag.
- Show environment variable key in usage (-h).
- Show environment variable value in usage as default value (-h) in order to confirm enviroment settings.
Use envflag.Parse() instead of flag.Parse().
Here is an example.
package main
import (
"flag"
"fmt"
"github.com/kouhin/envflag"
)
func main() {
var (
databaseMasterHost = flag.String("database-master-host", "localhost", "Database master host")
databaseMasterPort = flag.Int("database-master-port", 3306, "Database master port")
)
if err := envflag.Parse(); err != nil {
panic(err)
}
fmt.Println("RESULT: ", *databaseMasterHost, ":", *databaseMasterPort)
}Run DATABASE_MASTER_HOST=192.168.0.2 go run main.go -h you will get the following usage:
Usage of XXXX
-database-master-host="192.168.0.2": [DATABASE_MASTER_HOST] Database master host
-database-master-port=3306: [DATABASE_MASTER_PORT] Database master port
$go run main.go
RESULT: localhost : 3306
$export DATABASE_MASTER_HOST=192.168.0.2
$go run main.go
RESULT: 192.168.0.2 : 3306
$go run main.go -database-master-host=192.168.0.3
RESULT: 192.168.0.3 : 3306
You can customize envflag [Optional].
func main() {
ef := envflag.NewEnvFlag(
flag.CommandLine, // which FlagSet to parse
2, // min length
map[string]string{ // User-defined env-flag map
"MY_APP_ENV": "app-env",
},
true, // show env variable key in usage
true, // show env variable value in usage
)
var (
appEnv = flag.String("app-env", "dev", "Application env")
)
if err := ef.Parse(os.Args[1:]); err != nil {
panic(err)
}
fmt.Println("appEnv:", appEnv)
}Use envflag.SetDebugEnabled(true).