Graceful Shutdown in Golang

graceful_shutdown.go

package main

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

func main() {
	slog.Info(fmt.Sprintf("starting app on pid=%d\n", os.Getpid()))

	// create a channel to receive a os.Signal (type) with size of 1
	sigs := make(chan os.Signal, 1)

	// send to channel this signals
	signal.Notify(sigs, syscall.SIGTERM, syscall.SIGINT, syscall.SIGHUP)

	// starting the server in a go func
	srv := startServer()

	// app will wait here, waiting to receive a channel
	sig := <-sigs

	slog.Info(fmt.Sprintf("received signal=%s\n", sig))

	// create a context with timeout to wait server shutdown
	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()

	err := srv.Shutdown(ctx)

	if err != nil {
		slog.Error(err.Error())
	}

}

func startServer() *http.Server {
	mux := http.NewServeMux()
	mux.HandleFunc("/ping", PongHandler)

	srv := &http.Server{Addr: ":4000", Handler: mux}

	go func() {
		err := srv.ListenAndServe()
		slog.Info(fmt.Sprintf("server returned this error=%s\n", err))
	}()

	return srv
}

func PongHandler(response http.ResponseWriter, request *http.Request) {
	// a sleep to given you time to send signal
	time.Sleep(5 * time.Second)

	fmt.Fprintln(response, "pong")
}