func (l *LinkList) Add(item interface{}) (node *Node) {
	node = NewNode(item, l.First)
	l.First = node
	l.n++
	return
}
Add adds a new node to head, points to old head
package linklist
type Node struct {
	Item interface{}
	Next *Node
}
func NewNode(item interface{}, next *Node) *Node {
	return &Node{item, next}
}
type LinkList struct {
	First *Node
	n     int  
}
func NewLinkList() *LinkList {
	return &LinkList{nil, 0}
}