dependency injection pattern

di.go

package main

import (
	"net/http"
	"net/http/httptest"
)

func main() {
	m := mongo{}
	h := handler{d: m}
	http.ListenAndServe(":8080", h)
}


// package handler

type handler struct {
	d handler_dal
}

func (h handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	w.WriteHeader(http.StatusNoContent)
}


type handler_dal interface {
	Get(string) interface{}
}

type mockDal struct {

}

func (m mockDal) Get(string) interface{} {
	return nil
}

// *_test.go

func TestSomething() {
	//mdal := mockDal{/* mock */}
	mmdal := daltest_MockDal{}
	h := handler{d: mmdal}
	httptest.NewServer(h)
	
	// test 
}


// package dal

type dal interface {
	Get(string) interface{}
	Store(string, string) error
}

// package dal/mongo

type mongo struct {
}

func (m mongo) Get(string) interface{} {
	return nil
}
func (m mongo) Store(string, string) error {
	return nil
}


// package dal/daltest

type daltest_MockDal struct {
	
}

func (m daltest_MockDal) Get(string) interface{} {
	return nil
}
func (m daltest_MockDal) Store(string, string) error {
	return nil
}