update book code

eBook/examples/chapter_14/goroutine_select2.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"fmt"
+	"time"
+	"runtime"
+)
+
+func main() {
+	// setting GOMAXPROCS to 2 gives +- 22% performance increase, 
+	// but increasing the number doesn't increase the performance
+	// without GOMAXPROCS: +- 86000
+	// setting GOMAXPROCS to 2: +- 105000
+	// setting GOMAXPROCS to 3: +- 94000
+	runtime.GOMAXPROCS(2)
+	ch1 := make(chan int)
+	ch2 := make(chan int)
+	
+	go pump1(ch1)
+	go pump2(ch2)
+	go suck(ch1, ch2)
+	
+	time.Sleep(1e9)
+}
+
+func pump1(ch chan int) {
+	for i:=0; ; i++ {
+		ch <- i*2
+	}
+}
+
+func pump2(ch chan int) {
+	for i:=0; ; i++ {
+		ch <- i+5
+	}
+}
+
+func suck(ch1,ch2 chan int) {
+	for i := 0; ; i++ {
+		select {
+			case v := <- ch1:
+				fmt.Printf("%d - Received on channel 1: %d\n", i, v)
+			case v := <- ch2:
+				fmt.Printf("%d - Received on channel 2: %d\n", i, v)
+		}
+	}
+}
+
+