package main

import (
	"fmt"
	"sync"
)

const (
	goroutines = 10
	addsPerG   = 100
)

func main() {
	var (
		counter int
		mu      sync.Mutex
		wg      sync.WaitGroup
	)

	wg.Add(goroutines)
	for i := 0; i < goroutines; i++ {
		go func() {
			defer wg.Done()
			for j := 0; j < addsPerG; j++ {
				mu.Lock() // 进入临界区
				counter++
				mu.Unlock() // 离开临界区
			}
		}()
	}

	wg.Wait()
	fmt.Println("final counter:", counter)
}