new: pushed new graph experimental module

modules/graph/stack.go

@@ -0,0 +1,47 @@
+package graph
+
+import "sync"
+
+type entry struct {
+	data interface{}
+	next *entry
+}
+
+type Stack struct {
+	lock *sync.Mutex
+	head *entry
+	Size int
+}
+
+func (stk *Stack) Push(data interface{}) {
+	stk.lock.Lock()
+
+	element := new(entry)
+	element.data = data
+	temp := stk.head
+	element.next = temp
+	stk.head = element
+	stk.Size++
+
+	stk.lock.Unlock()
+}
+
+func (stk *Stack) Pop() interface{} {
+	if stk.head == nil {
+		return nil
+	}
+	stk.lock.Lock()
+	r := stk.head.data
+	stk.head = stk.head.next
+	stk.Size--
+
+	stk.lock.Unlock()
+
+	return r
+}
+
+func NewStack() *Stack {
+	stk := new(Stack)
+	stk.lock = &sync.Mutex{}
+	return stk
+}