Complete Guide to the sync Package in Go

The sync package in Go provides basic synchronization primitives like Mutex, WaitGroup, and Once to coordinate access to shared data across goroutines. Use sync.Mutex to protect critical sections, sync.WaitGroup to wait for a collection of goroutines to finish, and sync.Once to ensure a function runs exactly once.

package main

import (
	"fmt"
	"sync"
)

func main() {
	var mu sync.Mutex
	var wg sync.WaitGroup
	var once sync.Once
	count := 0

	wg.Add(3)
	for i := 0; i < 3; i++ {
		go func() {
			defer wg.Done()
			mu.Lock()
			count++
			mu.Unlock()
			if i == 0 {
				once.Do(func() { fmt.Println("Initialized once") })
			}
		}()
	}
	wg.Wait()
	fmt.Println("Final count:", count)
}

The sync package gives you tools to make sure multiple parts of your program don't step on each other's toes when running at the same time. Think of it like a traffic light system that ensures only one car (goroutine) enters an intersection (shared data) at a time, or a checklist that waits until all workers finish their tasks before closing the shop. You use it whenever you need to safely share data or coordinate timing between different threads of execution.