package main

import (

    "fmt"

    "runtime"

    "sync"

    "time"

)

func main() {

    runtime.GOMAXPROCS(4)

    testCond()

}

func testCond() {

    c := sync.NewCond(&sync.Mutex{})

    condition := false

    go func() {

        time.Sleep(time.Second * 1)

        c.L.Lock()                                //3 获得锁

        fmt.Println("[1] 变更condition状态,并发出变更通知.")

        condition = true

        c.Signal() //c.Broadcast()                //4 唤醒阻塞的main程，但是由于锁还没有释放，main抢不到锁会继续向下执行

        time.Sleep(1 * time.Second)

        fmt.Println("[1] 继续后续处理.")

        c.L.Unlock() //5 释放锁，main抢到锁，接着执行

    }()

    c.L.Lock()                                                     //1 先获得锁

    fmt.Println("[2] condition..........1")

    for !condition {

        fmt.Println("[2] condition..........2")

        //等待Cond消息通知

        c.Wait()                                            //2 阻塞main，释放锁

        fmt.Println("[2] condition..........3")                   //6 go程释放了锁 获得锁然后继续执行

    }

    fmt.Println("[2] condition..........4")

    c.L.Unlock()                                            //7解锁

    time.Sleep(1 * time.Second)

    fmt.Println("main end...")

}