update book code

eBook/examples/chapter_14/max_tasks.go

@@ -0,0 +1,31 @@
+package main
+
+const MAXREQS = 50
+var sem = make(chan int, MAXREQS)
+
+type Request struct {
+	a, b   int
+	replyc chan int
+}
+
+func process(r *Request) {
+	// do something
+}
+
+func handle(r *Request) {
+   sem <- 1    // doesn't matter what we put in it
+   process(r)  
+   <-sem       // one empty place in the buffer: the next request can start 
+}
+
+func server(service chan *Request) {
+   for {
+       request := <-service
+       go handle(request) 
+   }
+}
+
+func main() {
+	service := make(chan *Request)
+	go server(service)
+}