add english version

en/code/src/apps/ch.2.7/unbuffered_channel/main.go

@@ -0,0 +1,24 @@
+// Example code for Chapter 2.7 from "Build Web Application with Golang"
+// Purpose: Shows how to create and use a unbuffered channel
+package main
+
+import "fmt"
+
+func sum(a []int, c chan int) {
+	total := 0
+	for _, v := range a {
+		total += v
+	}
+	c <- total // send total to c
+}
+
+func main() {
+	a := []int{7, 2, 8, -9, 4, 0}
+
+	c := make(chan int)
+	go sum(a[:len(a)/2], c)
+	go sum(a[len(a)/2:], c)
+	x, y := <-c, <-c // receive from c
+
+	fmt.Println(x, y, x+y)
+}