use-cas.go

package main

import (
	"sync"
	"fmt"
	"sync/atomic"
)

var (
	balance int32 = 100
	wg = sync.WaitGroup{}
)

func main() {
	// expect: balance = 55
	var i int32
	for i = 0; i < 10; i++ {
		wg.Add(1)
		go withdraw(i)
	}
	wg.Wait()
	fmt.Println(balance)
}

func withdraw(amount int32) {
	for {
		if atomic.CompareAndSwapInt32(&balance, balance, balance - amount) {
			break
		}
	}
	wg.Done()
}