update book code

eBook/examples/chapter_14/chaining.go

@@ -0,0 +1,23 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+)
+
+var ngoroutine = flag.Int("n", 100000, "how many goroutines")
+
+func f(left, right chan int) { left <- 1+<-right }
+
+func main() {
+	flag.Parse()
+	leftmost := make(chan int)
+	var left, right chan int = nil, leftmost
+	for i := 0; i < *ngoroutine; i++ {
+		left, right = right, make(chan int)
+		go f(left, right)
+	}
+	right <- 0      // bang!
+	x := <-leftmost // wait for completion
+	fmt.Println(x)  // 100000, ongeveer 1,5 s
+}