Given a non-empty, singly linked list with head node `head`

, return a middle node of linked list.

If there are two middle nodes, return the second middle node.

**Example 1:**

Input:[1,2,3,4,5]

Output:Node 3 from this list (Serialization: [3,4,5]) The returned node has value 3. (The judge's serialization of this node is [3,4,5]). Note that we returned a ListNode object ans, such that: ans.val = 3, ans.next.val = 4, ans.next.next.val = 5, and ans.next.next.next = NULL.

Example 2:

Input:[1,2,3,4,5,6]

Output:Node 4 from this list (Serialization: [4,5,6]) Since the list has two middle nodes with values 3 and 4, we return the second one.

Note:The number of nodes in the given list will be between`1`

and`100`

.

**Solution：**

```
func middleNode(head *ListNode) *ListNode {
slow, fast := head, head;
for fast != nil && fast.Next != nil {
slow = slow.Next
fast = fast.Next.Next
}
return slow;
}
```