Understanding WaitGroup in Go (Golang)

WaitGroup is a struct that is part of sync package in Go. It is generally used to wait for a collection of goroutines to finish execution. The WaitGroup has below methods

• Add method to set the number of goroutines to wait for.

• Done method which is called by each of the goroutines when finished.

• Wait method which is used to block till all goroutines have finished and have called the Done method

Let’s see a working code:

package main

import (
    "fmt"
    "sync"
    "time"
)

func main() {
    var wg sync.WaitGroup
    wg.Add(2)
    go sleep(&wg, time.Second*1)
    go sleep(&wg, time.Second*2)
    wg.Wait()
    fmt.Println("All goroutines finished")
}

func sleep(wg *sync.WaitGroup, t time.Duration) {
    defer wg.Done()
    time.Sleep(t)
    fmt.Println("Finished Execution")
}

Output:

Finished Execution
Finished Execution
All goroutines finished