Compare and swap

Any time you test for a condition and act based on the result, you can create a race condition. For example, the following function does not prevent mutual exclusion, despite the use of atomics:

var locked sync.Bool
func wrongCriticalSectionExample() {
     if !locked.Load() {
          // Another goroutine may lock it now!
          locked.Store(true)
          defer locked.Store(false)
          // This goroutine enters critical section
          // but so can another goroutine
     }
}

The function starts by testing whether the atomic locked value is false. Two goroutines can execute this statement simultaneously, and seeing that it is false, both can enter the...