Hata döndürmek için Golang HTTP işleyicisini standartlaştırma

package main

import (
	"log"

	"random/http"
	"random/users"
)

func main() {
	rtr := http.NewRouter()
	rtr.Add("/api/v1/users", users.Handler)

	srv := http.NewServer(rtr.Handler, ":3000")
	log.Fatal(srv.ListenAndServe())
}

package http

import (
	"net/http"
)

func NewServer(handler http.Handler, address string) *http.Server {
	return &http.Server{
		Handler: handler,
		Addr:    address,
	}
}

package http

import "net/http"

type Router struct {
	Handler *http.ServeMux
}

func NewRouter() *Router {
	return &Router{
		Handler: http.NewServeMux(),
	}
}

func (r *Router) Add(path string, hnd handler) {
	r.Handler.Handle(path, handler(hnd))
}

package http

import (
	"errors"
	"fmt"
	"net/http"
)

type handler func(http.ResponseWriter, *http.Request) error

func (h handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	err := h(w, r)
	if err == nil {
		return
	}

	var e Error
	if !errors.As(err, &e) {
		w.WriteHeader(http.StatusInternalServerError)
		return
	}

	w.WriteHeader(e.Status)
	w.Write([]byte(fmt.Sprintf("code: %s, message: %s", e.Code, e.Error())))
}

package http

type Error struct {
	Status  int
	Code    string
	Message string
}

func (e Error) Error() string {
	return e.Message
}

package domain

import "random/http"

var (
	ErrInternalError    = http.Error{Status: 500, Code: "internal_error", Message: "An internal error has occurred"}
	ErrInvalidRequest   = http.Error{Status: 400, Code: "invalid_request", Message: "Request is invalid"}
	ErrResourceConflict = http.Error{Status: 409, Code: "resource_conflict", Message: "A resource conflict has been detected"}
	ErrResourceNotFound = http.Error{Status: 404, Code: "resource_not_found", Message: "Resource is not found"}
)

package users

import (
	"fmt"
	"net/http"
	"random/domain"
)

func Handler(w http.ResponseWriter, r *http.Request) error {
	id := r.Header.Get("id")
	if id == "" {
		return domain.ErrInvalidRequest
	}
	if id == "0" {
		return domain.ErrResourceNotFound
	}
	if id == "1" {
		return domain.ErrResourceConflict
	}

	w.WriteHeader(http.StatusOK)
	w.Write([]byte(fmt.Sprintf("I am user with id %s", id)))

	return nil
}