Why was the backend.Invoke call moved outside the mutex?

The call to backend.Invoke is moved outside the mutex to minimize the lock holding time and avoid blocking other goroutines for a long period.

If long or potentially blocking operations, such as network calls or external service requests, are performed inside a critical section (protected by a mutex), it will lead to reduced performance and possible deadlocks.

Therefore, the correct practice is to acquire the mutex only for accessing shared data or state, and then release it before calling long operations. This increases concurrency and responsiveness of the program.

Example:

mu.Lock()
state := sharedState
mu.Unlock()

result := backend.Invoke(state)

mu.Lock()
updateSharedState(result)
mu.Unlock()