Explain the use of Go's sync and atomicity primitives for ensuring the consistency and integrity of shared data among multiple goroutines in Go programs?
Go's sync package provides several synchronization primitives for controlling access to shared data and ensuring their consistency and integrity among multiple goroutines. These primitives include Mutex, RWMutex, WaitGroup, Once, Cond, and Pool.
**Mutex** is a mutual exclusion lock that allows only one goroutine to access a shared resource at a time. It has two methods:
**Lock()** acquires the lock, and
**Unlock()** releases the lock.
**RWMutex** is a reader-writer lock that allows multiple readers to access a shared resource concurrently but only one writer at a time. It has three methods:
**RLock()** acquires a read lock,
**RUnlock()** releases a read lock, and
**Lock()** acquires a write lock.
**WaitGroup** is used to wait for a group of goroutines to complete their execution before continuing. It has three methods:
**Add()** adds a number of goroutines to the wait group,
**Done()** signals that a goroutine has completed, and
**Wait()** blocks until all goroutines have completed.
**Once** is used to perform a task only once, regardless of how many times it is called from multiple goroutines. It has one method:
**Do()** executes a function only once.
**Cond** is a condition variable that allows goroutines to wait for a specific condition to become true. It has three methods:
**Wait()** blocks the calling goroutine until a signal is received,
**Signal()** signals one waiting goroutine, and
**Broadcast()** signals all waiting goroutines.
**Pool** is a concurrency-safe object pool that allows objects to be reused across multiple goroutines. It has two methods:
**Get()** returns a free object from the pool, and
**Put()** returns an object to the pool for reuse.
**sync/atomic** package provides atomic operations for basic data types such as integers and pointers. These operations ensure that access to shared variables is atomic and therefore consistent across multiple goroutines. The atomic operations include
**StoreInt64()**, among others.