Top view of binary tree using recursion in golang

Go program for Top view of binary tree using recursion. Here more information.

package main
import "fmt"
/* 
  Go program for
  Top view of binary tree using dfs
*/
// Binary Tree Node
type TreeNode struct {
	data int
	left * TreeNode
	right * TreeNode
}
func getTreeNode(data int) * TreeNode {
	// Set node value
	return  &TreeNode {data,nil,nil}
}
type BinaryTree struct {
	root * TreeNode
	level int
}
func getBinaryTree() * BinaryTree {
	// Set the initial value of root
	return &BinaryTree {nil,0}
}
// Print left side top nodes including root
func(this *BinaryTree) printleftSide(node * TreeNode, depth int) {
	if node != nil {
		if this.level < depth {
			// Print the resultant node
			fmt.Print("  ", node.data)
			this.level = depth
		}
		// Recursively
		// Visit left subtree
		this.printleftSide(node.left, depth + 1)
		// Visit right subtree
		this.printleftSide(node.right, depth - 1)
	}
}
// Print right side top nodes
func(this *BinaryTree) printRightSide(node * TreeNode, depth int) {
	if node != nil {
		if this.level < depth {
			// Print the resultant node
			fmt.Print("  ", node.data)
			this.level = depth
		}
		// Recursively
		// First visit right subtree
		this.printRightSide(node.right, depth + 1)
		// Then
		// Visit left subtree
		this.printRightSide(node.left, depth - 1)
	}
}
// This is handle the request of printing top view
func(this *BinaryTree) topView() {
	this.level = -1
	this.printleftSide(this.root, 0)
	this.level = 0
	this.printRightSide(this.root, 0)
}
func main() {
	// Create new tree
	var tree * BinaryTree = getBinaryTree()
	/*
	   Make A Binary Tree
	-----------------------
	         1
	       /   \
	      2     3
	     /     / \
	    4     5   6
	   /       \    
	  7         8    
	             \
	              9
	               \
	                10
	*/
	// Construct binary tree
	tree.root = getTreeNode(1)
	tree.root.left = getTreeNode(2)
	tree.root.right = getTreeNode(3)
	tree.root.right.right = getTreeNode(6)
	tree.root.right.left = getTreeNode(5)
	tree.root.left.left = getTreeNode(4)
	tree.root.left.left.left = getTreeNode(7)
	tree.root.right.left.right = getTreeNode(8)
	tree.root.right.left.right.right = getTreeNode(9)
	tree.root.right.left.right.right.right = getTreeNode(10)
	// Display top view
	tree.topView()
}

Output

 1  2  4  7  3  6  10