package main

import "sync"

func main() {
	for {
		x := 0
		y := 0
		a := 0
		b := 0

		var wg sync.WaitGroup

		wg.Add(1)
		go func() {
			y = 1
			a = x
			wg.Done()
		}()
		wg.Add(1)
		go func() {
			x = 1
			b = y
			wg.Done()
		}()
		wg.Wait()

		if a == 0 && b == 0 {
			println("Hello world!")
		}
	}
}