feature: add golang solution for leetcode 143

Author: hzliangbin

solution/0100-0199/0129.Sum Root to Leaf Numbers/Solution.go

@@ -0,0 +1,16 @@
+func sumNumbers(root *TreeNode) int {
+    if root == nil {
+        return 0
+    }
+    return dfs(root, 0)
+}
+
+func dfs(root *TreeNode, sum int) int {
+    if root == nil {
+        return 0
+    }
+    if root.Left == nil && root.Right == nil {
+        return 10*sum + root.Val
+    }
+    return dfs(root.Left, 10*sum + root.Val) + dfs(root.Right, 10*sum + root.Val)
+}