The read-write mutex

Go also supports a read-write lock. A read-write lock differentiates between read and write operations. So, whenever you only perform concurrent read operations, the goroutines won't block. However, whenever you perform a write operation, all other reads and writes get blocked until the write lock is released. As always, this is best explained with an example, such as the following code:

var myRWMutex = &sync.RWMutex{}

A read-write lock in Go is represented by a pointer to a Go struct of the sync.RWMutex type, which is what we initialized in the preceding code snippet.

To perform a read operation, we make use of the RLock() and RUnlock() methods of the Go struct:

myRWMutex.RLock()
fmt.Println(myMap[1])
myRWMutex.RUnlock()

To perform a write operation, we make use of the Lock() and Unlock() methods:

myRWMutex.Lock()
myMap[2] = 200
myRWMutex.Unlock()

The *sync.RWMutex type can be found all over the place in Go's standard package.