Subtraction of alternate nodes of linked list in golang

Go program for Subtraction of alternate nodes of linked list. Here problem description and other solutions.

package main
import "fmt"
/*
    Go program for
    Subtraction of the alternate nodes of linked list
*/
// Linked list node
type LinkNode struct {
	data int
	next * LinkNode
}
func getLinkNode(data int) * LinkNode {
	// return new LinkNode
	return &LinkNode {
		data,
		nil,
	}
}
type SingleLL struct {
	head * LinkNode
	tail * LinkNode
}
func getSingleLL() * SingleLL {
	// return new SingleLL
	return &SingleLL {
		nil,
		nil,
	}
}
func(this *SingleLL) insert(data int) {
	var node * LinkNode = getLinkNode(data)
	if this.head == nil {
		// Add first node
		this.head = node
	} else {
		// Add node at the end position
		this.tail.next = node
	}
	// New last node
	this.tail = node
}
// Display linked list element
func(this SingleLL) display() {
	if this.head == nil {
		return
	}
	var temp * LinkNode = this.head
	// iterating linked list elements
	for (temp != nil) {
		fmt.Print(" ", temp.data, " →")
		// Visit to next node
		temp = temp.next
	}
	fmt.Println(" NULL")
}
// Find the subtraction of all alternate 
// nodes in linked list
func(this SingleLL) alternateSubtraction() {
	// Define resultant variables
	var result int = 0
	var counter int = 0
	// Start to first node of linked list
	var temp * LinkNode = this.head
	// iterating linked list elements
	for (temp != nil) {
		if counter % 2 == 0 {
			// When get alternate node
			if result == 0 {
				result = temp.data
			} else {
				result = result - temp.data
			}
		}
		// Node counter
		counter++
		// Visit to next node
		temp = temp.next
	}
	fmt.Println(" Alternate nodes subtraction : ", result)
}
func main() {
	var sll * SingleLL = getSingleLL()
	// Add node in linked list
	// 4 → 7 → 2 → 9 → 1 → 3 → 4 → 3 → 6 → NULL
	sll.insert(4)
	sll.insert(7)
	sll.insert(2)
	sll.insert(9)
	sll.insert(1)
	sll.insert(3)
	sll.insert(4)
	sll.insert(3)
	sll.insert(6)
	// Display of linked list nodes
	sll.display()
	// Test
	sll.alternateSubtraction()
}

Output

 4 → 7 → 2 → 9 → 1 → 3 → 4 → 3 → 6 → NULL
 Alternate nodes subtraction : -9