tree traversal in go (recursively)

treeTraversal.go

package main

import (
	"fmt"
)

type TreeNode struct {
	Val   int
	Left  *TreeNode
	Right *TreeNode
}

func inorderTraversal(root *TreeNode) []int {
	if root == nil {
		return nil
	}
	output := []int{}
	output = append(output, inorderTraversal(root.Left)...)
	output = append(output, root.Val)
	output = append(output, inorderTraversal(root.Right)...)
	return output

}

func preorderTraversal(root *TreeNode) []int {
	if root == nil {
		return nil
	}
	output := []int{}
	output = append(output, root.Val)
	output = append(output, inorderTraversal(root.Left)...)
	output = append(output, inorderTraversal(root.Right)...)
	return output

}

func postorderTraversal(root *TreeNode) []int {
	if root == nil {
		return nil
	}
	output := []int{}
	output = append(output, inorderTraversal(root.Left)...)
	output = append(output, inorderTraversal(root.Right)...)
	output = append(output, root.Val)
	return output

}

func main() {
	root := TreeNode{Val: 1}
	root.Left = &TreeNode{Val: 2}
	root.Left.Left = &TreeNode{Val: 4}
	root.Right = &TreeNode{Val: 3}
	root.Right.Left = &TreeNode{Val: 5}
	root.Right.Right = &TreeNode{Val: 6}

	fmt.Println(inorderTraversal(&root))
	fmt.Println(preorderTraversal(&root))
	fmt.Println(postorderTraversal(&root))

}