test

test.go

@@ -0,0 +1,55 @@
+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
+		}
+	}
+}