1.11 程序优雅退出

package main

import (
	"fmt"
	"io"
	"log"
	"os"
	"os/signal"
	"syscall"
	"time"
)

var writer *os.File

func main() {

	// The file is opened as
	// a log file to write into.
	// This way we represent the resources
	// allocation.
	var err error
	writer, err = os.OpenFile(fmt.Sprintf("test_%d.log", time.Now().Unix()), os.O_RDWR|os.O_CREATE, os.ModePerm)
	if err != nil {
		panic(err)
	}

	// The code is running in a goroutine
	// independently. So in case the program is
	// terminated from outside, we need to
	// let the goroutine know via the closeChan
	closeChan := make(chan bool)
	go func() {
		for {
			time.Sleep(time.Second)
			select {
			case <-closeChan:
				log.Println("Goroutine closing")
				return
			default:
				log.Println("Writing to log")
				io.WriteString(writer, fmt.Sprintf("Logging access %s
", time.Now().String()))
			}

		}
	}()

	sigChan := make(chan os.Signal, 1)
	signal.Notify(sigChan,
		syscall.SIGTERM,
		syscall.SIGQUIT,
		syscall.SIGINT)

	// This is blocking read from
	// sigChan where the Notify function sends
	// the signal.
	<-sigChan

	// After the signal is received
	// all the code behind the read from channel could be
	// considered as a cleanup
	close(closeChan)
	releaseAllResources()
	fmt.Println("The application shut down gracefully")
}

func releaseAllResources() {
	io.WriteString(writer, "Application releasing all resources
")
	writer.Close()
}

/*

2018/03/17 23:05:10 Writing to log
2018/03/17 23:05:11 Writing to log
2018/03/17 23:05:12 Writing to log
2018/03/17 23:05:13 Writing to log
The application shut down gracefully
*/