Another Safe Enum in Go

roles.go

package main

import (
	"errors"
	"fmt"
)

type role string

const (
	Unknown   role = ""
	Member    role = "Member"
	Moderator role = "Moderator"
	Admin     role = "Admin"
)

func CreateUser(r interface{}) error {
	if _, ok := r.(role); !ok {
		return errors.New(fmt.Sprintf("Invalid user %#v", r))
	}

	fmt.Println("Creating user with role", r)
	return nil
}

func main() {
	err := CreateUser("foo")
	if err != nil {
		fmt.Println(err)
	}

	err = CreateUser(Admin)
	if err != nil {
		fmt.Println(err)
	}
}