Neat way to do configuration in Golang

play.go

package main

import (
	"encoding/json"
	"errors"
	"fmt"
	"reflect"

	"github.com/tidwall/gjson"
)

var v string = `
[
	{ "Type": "Alpha", "Omega": "Blah" },
	{ "Type": "Beta", "Gamma": "Hah" }
]
`

var types map[string]reflect.Type = map[string]reflect.Type{
	"Alpha": reflect.TypeOf(Alpha{}),
	"Beta":  reflect.TypeOf(Beta{}),
}

type Alpha struct {
	Omega string
}

type Beta struct {
	Gamma string
}

func main() {
	var opts []json.RawMessage
	err := json.Unmarshal([]byte(v), &opts)
	if err != nil {
		panic(err)
	}
	for _, o := range opts {
		x, err := Unmarshal(o)
		if err != nil {
			panic(err)
		}
		switch v := x.(type) {
		case *Alpha:
			fmt.Printf("Alpha: %v\n", v)
		case *Beta:
			fmt.Printf("Beta: %v\n", v)
		}
	}
}

func Unmarshal(raw json.RawMessage) (interface{}, error) {
	x := gjson.Get(string(raw), "Type")
	if typ, ok := types[x.Str]; ok {
		str := reflect.New(typ).Interface()
		err := json.Unmarshal([]byte(raw), &str)
		return str, err
	}
	return nil, errors.New("unknown type")
}