Hands-On System Programming with Go

Mutex

The most simple implementation of locker is sync.Mutex. Since its method has a pointer receiver, it should not be copied or passed around by value. The Lock() method takes control of the mutex if possible, or blocks the goroutine until the mutex becomes available. The Unlock() method releases the mutex and it returns a runtime error if called on a non-locked one.

Here is a simple example in which we launch a bunch of goroutines using the lock to see which is executed first:

func main() {    var m sync.Mutex    done := make(chan struct{}, 10)    for i := 0; i < cap(done); i++ {        go func(i int, l sync.Locker) {            l.Lock()            defer l.Unlock()            fmt.Println(i)            time.Sleep(time.Millisecond * 10)            done <- struct{}{}        }(i, &m)    } for i := 0; i < cap(done); i++ ...