Example of decorator pattern in GO

decorator.go

package main

import (
	"fmt"
	"log"
)

//Basic interface to be enriched
type GreetingsBot interface {
	DoHail(name string) (string, error)
}

//Nested functions not allowed so the function must be as type
type Hail func(name string) (string, error)

func (hail Hail) DoHail(name string) (string, error) {
	return hail(name)
}

//Enrich the interface without interference to original code
type Decorator func(bot GreetingsBot) GreetingsBot

//
func LogDecorator(component string) Decorator {
	return func(bot GreetingsBot) GreetingsBot {
		return Hail(func(name string) (string, error) {
			log.Printf("[%s] :Call logging", component)
			return bot.DoHail(name)
		})
	}
}

type EnglishBot struct{}

func (bot *EnglishBot) DoHail(name string) (string, error) {
	fmt.Printf("Hello %s \n", name)
	return "Hello", nil
}
func main() {

	helloBot := LogDecorator("Hailer")(&EnglishBot{})

	//helloBot is enriched client with Logging function
	helloBot.DoHail("Radek")
	helloBot.DoHail("Tereza")
	helloBot.DoHail("Tobias")
}