envconf

EnvConf

EnvConf is a Go package, for parsing configuration values from different sources.

Installing

go get github.com/antonmashko/envconf

Parse Configs

Usually you need a tag with desire configuration sources and execution of a single function envconf.Parse for getting all configuration values into your golang structure.

Supported configuration sources

• command line flags
• environment variables
• default values
• external sources (can be anything that is implementing interface External)

Supported tags

Tags:

• flag - name of flag;
• env - name of environment variable;
• default - if nothing set this value will be used as field value;
• required - on true checks that configuration exists in flag or env source;
• description - field description in help output.

Example

Let's take a look at a simple example. Here we're creating struct with 3 tags for different configuration sources: flag, env, and default value. NOTE: It's not necessary to specify tags for each configuration type, add desired only

package main

import (
	"fmt"

	"github.com/antonmashko/envconf"
)

type Example struct {
	Field1 string `flag:"flag-name" env:"ENV_VAR_NAME" default:"default-value"`
}

func main() {
	var cfg Example
	if err := envconf.Parse(&cfg); err != nil {
		panic(err)
	}
	fmt.Printf("%#v\n", cfg)
}

Testing! If you want to get set Field1 from command line flag, use flag name that is set in flag tag.

$ go run main.go -flag-name="variable-from-flag"
main.Example{Field1:"variable-from-flag"}

The same result would be for other configuration types.

-help output

Using envconf will also generate help output with all registered fields and types. Use flag -help or -h for getting it.

$ go run main.go -help

Usage:

Field1 <string> default-value
        flag: flag-name
        environment variable: ENV_VAR_NAME
        required: false
        description: ""

Configuration Priority

Priority:

1) Flag 
2) Environment variable 
3) External source
4) Default value