Basic golang http server with graceful shutdown

server.go

package main

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

	"github.com/golang/glog"
	"github.com/pkg/errors"
)

var (
	// http server flags
	httpAddress         = flag.String("http_address", "", "host or ip address for the http server.")
	httpPort            = flag.Int("http_port", 8080, "port for the http server.")
	httpShutdownTimeout = flag.Duration("http_shutdown_duration", 5*time.Second, "duration to allow for graceful http server shutdown.")
)

func handler(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "OK")
}

func main() {
	// Parse flags
	flag.Parse()

	http.HandleFunc("/", handler)

	addr := fmt.Sprintf("%s:%d", *httpAddress, *httpPort)
	srv := &http.Server{Addr: addr}

	// Create a channel to receive OS signals
	sigChan := make(chan os.Signal, 1)
	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)

	// Start the server in a goroutine
	go func() {
		glog.Infof("Listening on %s", addr)
		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
			glog.Errorf("Error starting server: %v\n", err)
			os.Exit(1)
		}
	}()

	// Block until a signal is received
	sig := <-sigChan
	glog.Infof("Received signal %s\n", sig)

	// Create a context to gracefully shutdown the server
	ctx, cancel := context.WithTimeout(context.Background(), *httpShutdownTimeout)
	defer cancel()

	// Attempt to shutdown the server
	if err := srv.Shutdown(ctx); err != nil {
		glog.Errorf("Error shutting down server: %v\n", err)
	}
	glog.Info("Server gracefully stopped")
}