[Go] Type, Method, and Interface

handler.go

type Handler interface {
       ServeHTTP(ResponseWriter, *Request)
}

type HandlerFunc func(ResponseWriter, *Request)

// ServeHTTP calls f(w, r).
func (f HandlerFunc) ServeHTTP(w ResponseWriter, r *Request) {              
      f(w, r)
}

i.go

package main

import (
	"fmt"
)

type MyHandler func(string)

type MyInterface interface {
	Foo()
}

type Aa string

func (a *Aa) Foo() {
	fmt.Println("Foo called : " + *a)
}

func (fs MyHandler) Foo() {
	fs("foo")
}

func CallFoo(i MyInterface) {
	i.Foo()
}

func main() {
	x := Aa("test")
	CallFoo(&x)

	var fs MyHandler 
	fs = func(s string) {
		fmt.Println("aaa:" + s)
	}

	CallFoo(&fs)
}