Go (golang) HTTP server with a simple connection limiter (max conn)

maxconn.go

package main

import (
	"context"
	"flag"
	"log"
	"net"
	"net/http"
	"os"
	"os/signal"
	"syscall"
	"time"

	"golang.org/x/net/netutil"
)

const (
	defaultBindAddr = ":8080"

	// defaultMaxConn is the default number of max connections the
	// server will handle. 0 means no limits will be set, so the
	// server will be bound by system resources.
	defaultMaxConn = 0
)

func main() {
	var (
		bindAddr string
		maxConn  uint64
	)

	flag.StringVar(&bindAddr, "b", defaultBindAddr, "TCP address the server will bind to")
	flag.Uint64Var(&maxConn, "c", defaultMaxConn, "maximum number of client connections the server will accept, 0 means unlimited")
	flag.Parse()

	router := http.NewServeMux()
	router.HandleFunc("/", handleRequest)

	srv := http.Server{
		ReadHeaderTimeout: time.Second * 5,
		ReadTimeout:       time.Second * 10,
		Handler:           router,
	}

	listener, err := net.Listen("tcp", ":8080")
	if err != nil {
		log.Fatal(err)
	}

	if maxConn > 0 {
		listener = netutil.LimitListener(listener, int(maxConn))

		log.Printf("max connections set to %d\n", maxConn)
	}
	defer listener.Close()

	log.Printf("listening on %s\n", listener.Addr().String())

	go func() {
		if err := srv.Serve(listener); err != nil && err != http.ErrServerClosed {
			log.Fatal(err)
		}
	}()

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

	log.Printf("interrupted, shutting down")

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

	if err := srv.Shutdown(ctx); err != nil {
		log.Printf("graceful shutdown failed: %v\n", err)
	}
}

func handleRequest(w http.ResponseWriter, r *http.Request) {
	log.Printf("got request from %s\n", r.RemoteAddr)

	w.WriteHeader(http.StatusOK)
	w.Write([]byte("you got it"))
}