Opinionated environment variable parser for Golang

The goal of this project is to make it easy to parse environment variables into complex configuration structures.

Highlights:

• Best effort parsing -- even if errors happened, the correctly defined/provided values will be parsed
• No (zero, none) external dependencies
• Support for most types (except complex) and pointers
• Support for list and embedded structs (or lists of structs)
• Custom prefix (default APP)
• Hardcoded (intentionally) separator _
• All errors reported in 1 (see helper functions)

Installation

To install and start using this package simply do:

$ go get -u -v github.com/akamensky/envparse

Usage

Here is basic example of parsing environment variables into configuration struct:

package main

import (
	"encoding/json"
	"fmt"
	"github.com/akamensky/envparse"
)

type config struct {
	Url      string `env:"name=someUrl,default=http://localhost:8080"`
	IntValue int    `env:"name=value_int,required"`
	ObjSlice []*Obj `env:"name=obj"`
}

type Obj struct {
	A string `env:"name=a"`
	B string `env:"name=b"`
}

func main() {
	c := &config{}
	fakeEnviron := []string{
		"APP_SOMEURL=https://github.com/akamensky/envparse",
		"APP_VALUEINT=456",
		"APP_OBJ_0_A=hello",
		"APP_OBJ_0_B=world",
		"APP_OBJ_1_A=it's a",
		"APP_OBJ_1_B=slice",
    }
	envparse.SetPrefix("APP")
	// Use os.Environ() to get list of environment variables
	if err := envparse.Parse(c, fakeEnviron); err != nil {
		panic(envparse.FullError(err))
	}
	b, err := json.MarshalIndent(c, "", "  ")
	if err != nil {
		panic(err)
    }
	fmt.Println(string(b))
}

Options

• name=<str> -- a name portion for this field in envvar
• required -- mark field as required, if no matching environment variable found will cause error to be returned (appended)
• default=<str> -- a way to define default value, cannot be provided for required fields. If both found, it will cause error to be added