Example of Go sync.WaitGroup

waitgroup.go

package main

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

func main() {
	var myWaitGroup sync.WaitGroup

	myWaitGroup.Add(2) // Must wait for 2 calls to 'done' before moving on

	go func(w *sync.WaitGroup) {
		fmt.Println("Start gorouting 1")
		fmt.Println("End gorouting 1")
		w.Done()
	}(&myWaitGroup)

	go func(w *sync.WaitGroup) {
		fmt.Println("Start gorouting 2")
		time.Sleep(time.Second * 3)
		fmt.Println("End gorouting 2")
		w.Done()
	}(&myWaitGroup)

	fmt.Println("Waiting for all goroutines to exit")
	myWaitGroup.Wait()
	fmt.Println("Waited for all goroutines to exit")
}

unnecessary to pass WaitGroup to goroutine, closure works fine.

@FelixSeptem you mean that the WaitGroup var is implicitly passed into the anonymous function as a pointer variable?
If so, indeed you could turn it into

func main() {
	var myWaitGroup sync.WaitGroup

	myWaitGroup.Add(2)

	go func() {
		fmt.Println("Start gorouting 1")
		fmt.Println("End gorouting 1")
		myWaitGroup.Done()
	}()

	go func() {
		fmt.Println("Start gorouting 2")
		time.Sleep(time.Second * 3)
		fmt.Println("End gorouting 2")
		myWaitGroup.Done()
	}()

	fmt.Println("Waiting for all goroutines to exit")
	myWaitGroup.Wait()
	fmt.Println("Waited for all goroutines to exit")
}

defer wg.Wait() is more resilient :)

👍 @prozz

defer wg.Wait() is more resilient :)

defer is have overhead (50-100ns)