add ch12_2

ch12/2/ch12_2.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"fmt"
+	"math/rand"
+)
+
+func PrintNumbers() {
+	const chNum = 2
+	firstCh := make(chan int, 10)
+	secondCh := make(chan int, 20)
+	defer close(firstCh)
+	defer close(secondCh)
+
+	go func() {
+		for j := 0; j < 10; j++ {
+			firstCh <- (rand.Int() % 100)
+		}
+	}()
+	go func() {
+		for j := 0; j < 10; j++ {
+			secondCh <- (rand.Int() % 100)
+		}
+	}()
+
+	i := 0
+forLoop:
+	for {
+		select {
+		case val1 := <-firstCh:
+			fmt.Printf("(%d) From first channel: %d\n", i+1, val1)
+		case val2 := <-secondCh:
+			fmt.Printf("(%d) From second channel: %d\n", i+1, val2)
+		}
+		i++
+		if i == chNum*10 {
+			break forLoop
+		}
+	}
+}
+
+func main() {
+	PrintNumbers()
+}