Go Systems Programming

Using sync.RWMutex

Go offers another type of mutex, called sync.RWMutex, that allows multiple readers to hold the lock but only a single writer - sync.RWMutex is an extension of sync.Mutex that adds two methods named sync.RLock and sync.RUnlock, which are used for locking and unlocking for reading purposes. Locking and unlocking a sync.RWMutex for exclusive writing should be done with Lock() and Unlock(), respectively.

This means that either one writer can hold the lock or multiple readers: not both! You will most likely use such a mutex when most of the goroutines want to read a variable and you do not want goroutines to wait in order to get an exclusive lock.

In order to demystify sync.RWMutex a little, you should discover that the sync.RWMutex ...