Which of the list are synchronization tools in Go? Channels, sync.WaitGroup, sync.Mutex, sync.Cond?.

In Go, the listed synchronization tools are:

• Channels: the primary and idiomatic way to synchronize and exchange data between goroutines.
• sync.WaitGroup: used to wait for a group of goroutines to finish.
• sync.Mutex: provides mutual exclusion to protect critical sections.
• sync.Cond: a conditional variable for more complex synchronization, such as waiting for a certain state.

All of these are synchronization tools in Go. They are used in different scenarios:

• Channels are good for data transfer and signaling.
• Mutexes are for protecting shared resources.
• WaitGroup is for waiting for multiple goroutines to complete.
• Cond is for implementing waiting and notification upon state changes.

Example of using WaitGroup and Mutex:

var mu sync.Mutex
var wg sync.WaitGroup
counter := 0

wg.Add(2)
go func() {
    defer wg.Done()
    mu.Lock()
    counter++
    mu.Unlock()
}()
go func() {
    defer wg.Done()
    mu.Lock()
    counter++
    mu.Unlock()
}()
wg.Wait()
fmt.Println(counter) // 2