go: add «876. Middle of the Linked List»

Signed-off-by: Matej Focko <mfocko@redhat.com>

go/middle-of-the-linked-list.go

@@ -0,0 +1,20 @@
+package middle_of_the_linked_list
+
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func middleNode(head *ListNode) *ListNode {
+	x := head
+	y := head
+
+	for y != nil && y.Next != nil {
+		x = x.Next
+		y = y.Next.Next
+	}
+
+	return x
+}