Can you explain what mutual exclusion (Mutex) is and how it works?

Mutual exclusion (Mutex) is a synchronization mechanism that guarantees that at any given moment, only one goroutine (thread) can access a specific resource or critical section of code.

In Go, this is achieved using the sync.Mutex type. When a goroutine calls Lock(), it locks the mutex, and other goroutines attempting to call Lock() will wait until the mutex is unlocked by calling Unlock().

Example:

var mu sync.Mutex
var counter int

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

In this example, increment safely increases the value of counter, preventing concurrent access from multiple goroutines.