sync.Mutex vs sync.RWMutex

When working with concurrent programs in Go, controlling access to shared data is crucial. That’s where sync.Mutex and sync.RWMutex come in.

1. sync.Mutex

A Mutex (short for mutual exclusion lock) is the simplest locking mechanism.

It allows only one goroutine to access a resource at a time.

If one goroutine has locked the mutex, all others trying to lock it will block until it’s unlocked.

Usage:

Lock(): acquire exclusive access

Unlock(): release the lock

When to use:

• When modifying (writing) shared data.
• Only one goroutine can hold the lock at a time.
• Blocks all readers and writers.

2. sync.RWMutex

An RWMutex (read–write mutex) allows multiple readers at the same time — but only one writer, and writers block readers.

Usage:

RLock(): acquire shared access for reading

RUnlock(): release shared read lock

Lock() / Unlock(): exclusive access for writing

When to use:

• Use RLock() when reading shared data.
• Multiple readers can hold it simultaneously.
• Writers are blocked until all readers release their locks.