Snippet

Coordinating Multiple Goroutines with sync.WaitGroup

The sync.WaitGroup is used to coordinate execution flow when starting multiple concurrent tasks in separate goroutines. By calling Add(1) before starting a goroutine and Done() when it exits, we manage a counter of active routines. Wait() blocks execution until this counter drops to zero, guaranteeing that subsequent code runs only after all tasks have finished.

snippet.go

package main
 
import (
	"fmt"
	"sync"
	"time"
)
 
func performTask(taskID int, wg *sync.WaitGroup) {
	defer wg.Done()
	fmt.Printf("Starting task %d\n", taskID)
	time.Sleep(100 * time.Millisecond)
	fmt.Printf("Finished task %d\n", taskID)
}
 
func coordinateTasks() {
	var wg sync.WaitGroup
	for i := 1; i <= 3; i++ {
		wg.Add(1)
		go performTask(i, &wg)
	}
	wg.Wait()
	fmt.Println("All concurrent tasks completed successfully.")
}

Breakdown

var wg sync.WaitGroup

Declares a Group variable that holds the internal counter of goroutines to wait for.

wg.Add(1)

Increments the WaitGroup counter. This must be executed in the main goroutine before starting the sub-goroutine.

defer wg.Done()

Ensures the counter is decremented when the goroutine finishes, even if it exits early.

wg.Wait()

Blocks the current execution block until the internal WaitGroup counter reaches zero.

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Coordinating Multiple Goroutines with sync.WaitGroup

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