func (n *Node) GetKey() string {
	return n.key
}
GetKey returns the node's key
package hash
type Node struct {
	key  string
	val  interface{}
	next *Node
}
type List struct {
	head, tail *Node
	size       int
}
func NewList() *List {
	return &List{size: 0}
}
func (l *List) GetHead() *Node {
	return l.head
}
func (l *List) GetTail() *Node {
	return l.tail
}
func (n *Node) Next() *Node {
	if n == nil {
		return nil
	}
	return n.next
}