http server in go

package main

import (
	"context"
	"log"
	"net/http"
	"os"
	"os/signal"
	"time"
)

type server struct {
	rtr *http.ServeMux
}

func newServer() *server {
	s := &server{rtr: http.NewServeMux()}
	s.routes()
	return s
}

func (s *server) routes() {
	s.rtr.HandleFunc("/about", s.handleAbout())
	s.rtr.HandleFunc("/", s.handleIndex())
	s.rtr.HandleFunc("/admin", s.adminOnly(s.handleAdminIndex()))
}
func (s *server) handleAbout() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte("about me\n"))
	}
}

func (s *server) handleIndex() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte("main index\n"))
	}
}

func (s *server) handleAdminIndex() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte("admin only\n"))
	}
}

func (s *server) adminOnly(h http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if true { //!currentUser(r).IsAdmin {
			http.NotFound(w, r)
			return
		}
		h(w, r)
	}
}

func (s server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("server", ".me")
	s.rtr.ServeHTTP(w, r)
}

func main() {
	h := &http.Server{Addr: ":8080", Handler: newServer()}
	lg := log.New(os.Stdout, "", 0)
	go func() {
		lg.Println("Listening :8080")
		if err := h.ListenAndServe(); err != nil {
			lg.Fatal(err)
		}
	}()

	stop := make(chan os.Signal, 1)
	signal.Notify(stop, os.Interrupt)
	<-stop

	lg.Println("Shutting down the server ...")
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()
	if err := h.Shutdown(ctx); err != nil {
		lg.Fatal(err)
	}
	lg.Printf("Server stopped gracefully ...")
}

func TestHandleAbout(t *testing.T) {
	is := is.New(t)
	srv := server{
		db:    mockDatabase,
		email: mockEmailSender,
	}
	srv.routes()
	req, err := http.NewRequest("GET", "/about", nil)
	is.NoErr(err)
	w := httptest.NewRecorder()
	srv.ServeHTTP(w, req)
	is.Equal(w.StatusCode, http.StatusOK)
}