update book code

eBook/exercises/chapter_11/main_stack.go

@@ -0,0 +1,29 @@
+// main_stack.go
+package main
+
+import (
+	"fmt"
+	"./stack/stack"
+)
+
+var st1 stack.Stack
+
+func main() {
+	st1.Push("Brown")
+	st1.Push(3.14)
+	st1.Push(100)
+	st1.Push([]string{"Java", "C++", "Python", "C#", "Ruby"})
+	for {
+		item, err := st1.Pop()
+		if err != nil {
+			break
+		}
+		fmt.Println(item)
+	}
+}
+/* Output:
+[Java C++ Python C# Ruby]
+100
+3.14
+Brown
+*/