2.8 sync.Mutex

1. Mutex是什么

• 互斥锁
• 实现了Locker接口，zero-value是没加锁的状态
• 加锁解锁可以在不同的goroutine中

2. 使用

2.1. 不使用Mutex的情况

const TIMES = 1000

var data int = 0

func TestSync2(t *testing.T) {
	var wg sync.WaitGroup
	wg.Add(2)
	go func() {
		defer wg.Done()
		for i := 0; i < TIMES; i++ {
			data--
			time.Sleep(2*time.Millisecond)
		}
	}()

	go func() {
		defer wg.Done()
		for i := 0; i < TIMES; i++ {
			data++
			time.Sleep(time.Millisecond)
		}
	}()

	wg.Wait()
	fmt.Println(data, data == 0)
}
//输出
-1 false

2.2. 使用Mutex的情况

const TIMES = 1000

var data int = 0

func TestSync2(t *testing.T) {
	var wg sync.WaitGroup
	var lock sync.Mutex
	wg.Add(2)
	go func() {
		defer wg.Done()
		for i := 0; i < TIMES; i++ {
			lock.Lock()
			data--
			lock.Unlock()
			time.Sleep(2 * time.Millisecond)
		}
	}()

	go func() {
		defer wg.Done()
		for i := 0; i < TIMES; i++ {
			lock.Lock()
			data++
			lock.Unlock()
			time.Sleep(time.Millisecond)
		}
	}()

	wg.Wait()
	fmt.Println(data, data == 0)
}


//输出
0 true