Morris preorder traversal in golang

Go program for Morris preorder traversal. Here problem description and explanation.

package main
import "fmt"
/* 
  Go program for
  Morris traversal preorder
*/
// Binary Tree Node
type TreeNode struct {
	data int
	left * TreeNode
	right * TreeNode
}
func getTreeNode(data int) * TreeNode {
	// return new TreeNode
	return &TreeNode {data,nil,nil}
}
type BinaryTree struct {
	root * TreeNode
}
func getBinaryTree() * BinaryTree {
	// return new BinaryTree
	return &BinaryTree {nil}
}
//  Recursive function
// Display preorder view of binary tree
func(this BinaryTree) preorder(node * TreeNode) {
	if node != nil {
		// Print node value
		fmt.Print("  ", node.data)
		this.preorder(node.left)
		this.preorder(node.right)
	}
}
// iterative preorder tree traversal
func(this BinaryTree) morrisPreorder() {
	if this.root == nil {
		return
	}
	var current * TreeNode = this.root
	var auxiliary * TreeNode = nil
	// iterating tree nodes
	for (current != nil) {
		if current.left == nil {
			// Print node value
			fmt.Print("  ", current.data)
			// Visit to right childs
			current = current.right
		} else {
			auxiliary = current.left
			// Find rightmost node which is not
			// equal to current node
			for (auxiliary.right != nil && 
				auxiliary.right != current) {
				// Visit to right subtree
				auxiliary = auxiliary.right
			}
			if auxiliary.right != current {
				// Print node value
				fmt.Print("  ", current.data)
				// Connect rightmost right node to current node
				auxiliary.right = current
				// Visit to left childs
				current = current.left
			} else {
				// unlink
				auxiliary.right = nil
				// Visit to right child
				current = current.right
			}
		}
	}
	fmt.Print("\n")
}
func main() {
	// Create new tree
	var tree * BinaryTree = getBinaryTree()
	/*
	Create Binary Tree
	         4
	       /   \
	      8     10
	     / \   /  \
	    1   6 7   -3
	       /
	      9
	*/
	// Add tree node
	tree.root = getTreeNode(4)
	tree.root.left = getTreeNode(8)
	tree.root.left.left = getTreeNode(1)
	tree.root.right = getTreeNode(10)
	tree.root.right.right = getTreeNode(-3)
	tree.root.right.left = getTreeNode(7)
	tree.root.left.right = getTreeNode(6)
	tree.root.left.right.left = getTreeNode(9)
	fmt.Println("\n Recursive Preorder")
	// Display preorder elements
	tree.preorder(tree.root)
	fmt.Println("\n Morris Preorder")
	tree.morrisPreorder()
}

Output

 Recursive Preorder
 4  8  1  6  9  10  7  -3
 Morris Preorder
 4  8  1  6  9  10  7  -3