Wait for goroutines Using WaitGroups -

Syntax

A sync.WaitGroup waits for a group of goroutines to finish.

var wg sync.WaitGroup
wg.Add(2)

go func() {
        // Do work
        wg.Done()
}()

go func() {
        // Do work
        wg.Done()
}()

wg.Wait()

First the main goroutine calls Add to set the number of goroutines to wait for.
Then two new goroutines run and call Done when finished.

At the same time, Wait is used to block until these two goroutines have finished.

Note: A WaitGroup must not be copied after first use.

Example - Play with 1 WaitGroup

func main() {
  var waitGroup sync.WaitGroup

  waitGroup.Add(1) // 1 because we will be executing 1 goroutine
  go func() {      // Goroutine
    printStrFiveTimes("नमस्ते किंशुक") // Call our func inside goroutine

    // Below line will decrement the counter in waitGroup
    waitGroup.Done() // Notify waitGroup that our func is done executing
  }()

  waitGroup.Wait() // Wait for goroutines to finish their execution
}

func printStrFiveTimes(str string) {
  for i := 1; i <= 5; i++ {
    fmt.Printf("%2v %v\n", i, str)
    time.Sleep(time.Millisecond * 500)
  }
}

Output:

 1 नमस्ते किंशुक
 2 नमस्ते किंशुक
 3 नमस्ते किंशुक
 4 नमस्ते किंशुक
 5 नमस्ते किंशुक

goroutine wait-group

Syntax

Example - Play with 1 WaitGroup

See also