What types of mutual exclusions (Mutex) are implemented in the standard Go library?

The standard library of Go implements a primary mutual exclusion type — sync.Mutex. It is a simple mutex that provides locking and unlocking to protect critical sections of code from concurrent access.

Additionally, there is sync.RWMutex — an extended version of the mutex that allows multiple readers to hold the lock simultaneously, but writing is blocked exclusively.

Example of using sync.Mutex:

var mu sync.Mutex
var counter int

func increment() {
    mu.Lock()
    defer mu.Unlock()
    counter++
}

And an example with sync.RWMutex:

var rwMu sync.RWMutex
var data int

func readData() int {
    rwMu.RLock()
    defer rwMu.RUnlock()
    return data
}

func writeData(val int) {
    rwMu.Lock()
    defer rwMu.Unlock()
    data = val
}