*http.Server in Go 1.8 supports graceful shutdown. This is a small example.

graceful.go

package main

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

type Server struct {
	logger *log.Logger
	mux    *http.ServeMux
}

func NewServer(options ...func(*Server)) *Server {
	s := &Server{
		logger: log.New(os.Stdout, "", 0),
		mux:    http.NewServeMux(),
	}

	for _, f := range options {
		f(s)
	}

	s.mux.HandleFunc("/", s.index)

	return s
}

func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	s.mux.ServeHTTP(w, r)
}

func (s *Server) index(w http.ResponseWriter, r *http.Request) {
	s.logger.Println("GET /")

	w.Write([]byte("Hello, World!"))
}

func main() {
	stop := make(chan os.Signal, 1)

	signal.Notify(stop, os.Interrupt)

	logger := log.New(os.Stdout, "", 0)

	addr := ":" + os.Getenv("PORT")
	if addr == ":" {
		addr = ":2017"
	}

	s := NewServer(func(s *Server) { s.logger = logger })

	h := &http.Server{Addr: addr, Handler: s}

	go func() {
		logger.Printf("Listening on http://0.0.0.0%s\n", addr)

		if err := h.ListenAndServe(); err != nil {
			logger.Fatal(err)
		}
	}()

	<-stop

	logger.Println("\nShutting down the server...")

	ctx, _ := context.WithTimeout(context.Background(), 5*time.Second)

	h.Shutdown(ctx)

	logger.Println("Server gracefully stopped")
}

Hi, great contribution.

There is one thing that could make it more complete in my opinion.

Everywhere this code is, it will always print "Listening on http://...." in the console, even if ListenAndServe() was unable to start actually listening.

	log.Printf("Listening on http://0.0.0.0%s\n", hs.Addr)

	if err := hs.ListenAndServe(); err != http.ErrServerClosed {
		log.Fatal(err)
	}

If you start 1 server, you'll see this in the console:

Listening on http://0.0.0.0:2017

If you start a 2nd server without shutting down the 1st one, you will see this in the console:

Listening on http://0.0.0.0:2017
panic... listen tcp :2017: bind: address already in use

So it first shows "Listening on http://..." however this never actually happened.

I'm not a go expert, is there a way to implement this?

-- UPDATE

Apparently using http.Listen and http.Serve individually, it is possible to catch a port in use error (or any other error while trying to listen to a tcp network) before assuming the server is listening.

Source: https://stackoverflow.com/a/48250354/194630

	listener, err := net.Listen("tcp", ":"+config.Port)
	if err != nil {
		log.Fatal(err)
	}

	done := make(chan bool)
	go server.Serve(listener)

	// Log server started
	log.Printf("Server started at port %v", config.Port)
	<-done