Added a package test.

hello.go

@@ -1,7 +1,17 @@
 package main
 
-import "fmt"
+import(
+    "../src/lib/"
+    "fmt"
+)
 
 func main() {
-    fmt.Printf("Hello, World")
+    var s collection.Stack
+    s.Push("world")
+    s.Push("hello, ")
+    for s.Size() > 0 {
+        fmt.Print(s.Pop())
+    }
+    fmt.Println()
+    // Output: hello, world
 }

helloStack.go

@@ -0,0 +1,17 @@
+package collection_test
+
+import (
+    collection "."
+    "fmt"
+)
+
+func Example() {
+    var s collection.Stack
+    s.Push("world")
+    s.Push("hello, ")
+    for s.Size() > 0 {
+        fmt.Print(s.Pop())
+    }
+    fmt.Println()
+    // Output: hello, world
+}

lib/stack.go

@@ -0,0 +1,27 @@
+// Package collection implements a generic stack.
+package collection
+
+// The zero value for Stack is an empty stack ready to use.
+type Stack struct {
+    data []interface{}
+}
+
+// Push adds x to the top of the stack.
+func (s *Stack) Push(x interface{}) {
+    s.data = append(s.data, x)
+}
+
+// Pop removes and returns the top element of the stack.
+// It’s a run-time error to call Pop on an empty stack.
+func (s *Stack) Pop() interface{} {
+    i := len(s.data) - 1
+    res := s.data[i]
+    s.data[i] = nil  // to avoid memory leak
+    s.data = s.data[:i]
+    return res
+}
+
+// Size returns the number of elements in the stack.
+func (s *Stack) Size() int {
+    return len(s.data)
+}