经典并发题目

现在有4个协程，分别对应编号为1,2,3,4,每秒钟就有一个协程打印自己的编号，要求编写一个程序，让输出的编号总是按照1,2,3,4,1,2,3,4这样的规律一直打印下去

type Token struct {
}func newWorker(id int, ch chan Token, nextCh chan Token) {for {token := <-chfmt.Println(id + 1)time.Sleep(time.Second)nextCh <- token}
}func testGoroutine() {chs := []chan Token{make(chan Token), make(chan Token), make(chan Token), make(chan Token)}for i := 0; i < 4; i++ {go newWorker(i, chs[i], chs[(i+1)%4])}chs[0] <- struct{}{}select {}
}

信号通知题目

使用chan来实现程序的graceful shutdown，在程序退出之前来执行一些连接的关闭，文件的close相关操作。

func testClosed() {var closing = make(chan struct{})var closed = make(chan struct{})go func() {for {select {case <-closing:returndefault:time.Sleep(100 * time.Millisecond)}}}()termChan := make(chan os.Signal)signal.Notify(termChan, syscall.SIGINT, syscall.SIGTERM)<-termChanclose(closing)go doCleanUp(closed)select {case <-closed:case <-time.After(time.Second):fmt.Println("clean timeout")}fmt.Println("gracefully exit")
}func doCleanUp(closed chan struct{}) {time.Sleep(time.Minute)close(closed)
}