main.go for k8s app

main.go

package main

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

func main() {
	srv := &http.Server{
		Addr: ":8080",
		// ...
	}
	go func() {
		if err := srv.ListenAndServe(); err != http.ErrServerClosed {
			log.Fatal(err)
		}
	}()

	var (
		ready   = true
		muReady sync.RWMutex
	)

	// health check
	go func() {
		m := http.NewServeMux()
		m.HandleFunc("/readiness", func(w http.ResponseWriter, r *http.Request) {
			muReady.RLock()
			ready := ready
			muReady.RUnlock()
			if ready {
				w.WriteHeader(http.StatusOK)
				return
			}
			w.WriteHeader(http.StatusServiceUnavailable)
		})
		m.HandleFunc("/liveness", func(w http.ResponseWriter, r *http.Request) {
			w.WriteHeader(http.StatusOK)
		})
		if err := http.ListenAndServe(":18080", m); err != nil {
			log.Println("can not start healthcheck server")
		}
	}()

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

	muReady.Lock()
	ready = false
	muReady.Unlock()
	time.Sleep(5 * time.Second) // >= periodSeconds * failureThreshold

	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	if err := srv.Shutdown(ctx); err != nil {
		log.Println("server shutdown error:", err)
		return
	}
	log.Println("server shutdown")
}