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.