package main

import (
	"fmt"
	"log"
	"os"
	"sync"
	"time"
)

func sendA(ch chan string) {
	fmt.Println("start waiting A")
	time.Sleep(20 * time.Second)
	fmt.Println("end waiting A")
	ch <- "a"
	close(ch)
}

func sendB(ch chan string) {
	fmt.Println("start waiting B")
	time.Sleep(10 * time.Second)
	fmt.Println("end waiting B")
	ch <- "b"
	close(ch)
}

func main() {
	if err := os.Chdir(""); err != nil {
		fmt.Println("didn't change directory")
	}
	wg := sync.WaitGroup{}
	wg.Add(2)
	chA := make(chan string)
	chB := make(chan string)
	fmt.Println("start sendA")
	go sendA(chA)
	fmt.Println("start sendB")
	go sendB(chB)
	fmt.Println("start printing A")
	go printCock(chA, &wg)
	fmt.Println("start printing B")
	go printCock(chB, &wg)
	wg.Wait()
}

func printCock(ch chan string, wg *sync.WaitGroup) {
	for {
		select {
		case x := <-ch:
			log.Println(x)
			wg.Done()
			return
		}
	}
}