Mutex

Mutex Locking

Mutex locking in Go allows you to ensure that only one goroutine at a time has a lock:

import "sync"

func mutexTest() {
    lock := sync.Mutex{}
    go func(m *sync.Mutex) {
        m.Lock()
        defer m.Unlock()   // Automatically unlock when this function returns
        // Do some things
    }(&lock)

    lock.Lock()
    // Do some other things
    lock.Unlock()
}

Using a Mutex allows you to avoid race conditions, concurrent modifications, and other issues associated with multiple concurrent routines operating on the same resources. Note that Mutex.Unlock() can be executed by any routine, not just the routine that got the lock. Also note that the call to Mutex.Lock() will not fail if another routine holds the lock; it will block until the lock is released.

Tip: Whenever you’re passing a Mutex variable to a function, always pass it as a pointer. Otherwise a copy is made of your variable, which defeats the purpose of the Mutex. If you’re using an older Go version (< 1.7), the compiler will not warn you about this mistake!