main.go

package main

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"time"

	"go.mongodb.org/mongo-driver/bson"
)

func loggingHandler(next http.Handler) http.Handler {
	fn := func(w http.ResponseWriter, r *http.Request) {
		t1 := time.Now()
		next.ServeHTTP(w, r)
		t2 := time.Now()
		log.Printf("[%s] %q %v\n", r.Method, r.URL.String(), t2.Sub(t1))
	}

	return http.HandlerFunc(fn)
}

func recoverHandler(next http.Handler) http.Handler {
	fn := func(w http.ResponseWriter, r *http.Request) {
		defer func() {
			if err := recover(); err != nil {
				log.Printf("panic: %+v", err)
				http.Error(w, http.StatusText(500), 500)
			}
		}()

		next.ServeHTTP(w, r)
	}

	return http.HandlerFunc(fn)
}

func aboutHandler(w http.ResponseWriter, r *http.Request) {
	// fmt.Fprintf(w, "You are on the about page.")
	body, err := ioutil.ReadAll(r.Body)
	if err != nil {
		http.Error(w, "Can't read body", http.StatusBadRequest)
		return
	}

	var object bson.M
	json.Unmarshal(body, &object)

	log.Print(object["tal"].(int64))
}

func indexHandler(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "Welcome!")
}

type Constructor func(http.Handler) http.Handler

type Chain struct {
	constructors []Constructor
}

func New(constructors ...Constructor) Chain {
	return Chain{append(([]Constructor)(nil), constructors...)}
}

func (c Chain) Then(h http.Handler) http.Handler {
	if h == nil {
		h = http.DefaultServeMux
	}

	for i := range c.constructors {
		h = c.constructors[len(c.constructors)-1-i](h)
	}

	return h
}

func main() {
	commonHandlers := New(loggingHandler, recoverHandler)
	http.Handle("/", commonHandlers.Then(http.HandlerFunc(indexHandler)))
	http.Handle("/about", commonHandlers.Then(http.HandlerFunc(aboutHandler)))

	http.ListenAndServe(":8080", nil)
}