Graceful Shutdown example

graceful-shutdown.go

package main

import (
	"context"
	"fmt"
	"os"
	"os/signal"
	"strconv"
	"syscall"
	"time"
)

func main() {
	ctx := context.Background()
	ctx, cancel := context.WithCancel(ctx)

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

	defer func() {
		signal.Stop(sigCh)
		cancel()
	}()

	go func() {
		select {
		case sig := <-sigCh:
			fmt.Printf("[warning] Got signal %s, trying to shutdown gracefully...\n", sig.String())
			cancel()
		case <-ctx.Done():
			fmt.Printf("process is quitting normally\n")
		}
	}()

	if err := run(ctx, os.Args[1:]); err != nil {
		fmt.Fprintf(os.Stderr, "%+v\n", err)
		os.Exit(1)
	}
}

func run(ctx context.Context, args []string) error {
	parseInt := func(s string) int {
		v, err := strconv.Atoi(s)
		if err != nil {
			panic(err)
		}
		return v
	}
	interval := parseInt(args[0])
	count := parseInt(args[1])
	fmt.Printf("interval: %d, count: %d\n", interval, count)

	fmt.Printf("Run ' kill -TERM %d ' to stop\n", os.Getpid())

	for i := 0; i < count; i++ {
		select {
		case <-ctx.Done():
			fmt.Printf("run function is quitting by ctx.Done() \n")
			// return fmt.Errorf("run function is stopped")
			return ctx.Err()
		default:
		}
		fmt.Printf("run function is running... %d\n", i)
		time.Sleep(time.Duration(interval) * time.Second)
	}

	fmt.Printf("run function is quitting normally\n")
	return nil
}