Sum of Left Leaves Solutions in Go

package leetcode

import (
	"github.com/halfrost/LeetCode-Go/structures"
)

// TreeNode define
type TreeNode = structures.TreeNode

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */

func sumOfLeftLeaves(root *TreeNode) int {
	if root == nil {
		return 0
	}
	if root.Left != nil && root.Left.Left == nil && root.Left.Right == nil {
		return root.Left.Val + sumOfLeftLeaves(root.Right)
	}
	return sumOfLeftLeaves(root.Left) + sumOfLeftLeaves(root.Right)
}