Trying to make a binary search tree, but I keep getting invalid memory address or nil pointer dereference errors

Question

I'm trying to create a BST, add a node, and print the data in that node, but I keep getting invalid memory address or nil pointer dereference errors. I know something is wrong with my pointers, and I've been fiddling around with them all afternoon, and I can't seem to get it right. Could someone please take a look and let me know what stupid mistake I'm making?

package main

import "fmt"

type node struct {
    data  int
    left  *node
    right *node
}

type root struct {
    root *node
}

func (bt root) addNode(n *node, data int) {
    if n == nil {
        newNode := node{
            data:  data,
            left:  nil,
            right: nil,
        }
        n = &newNode
        fmt.Println("Works")
    } else if data < n.data {
        bt.addNode(n.left, data)
    } else {
        bt.addNode(n.right, data)
    }
}

func main() {
    tree := root{root: nil}

    tree.addNode(tree.root, 6)
    fmt.Println(tree.root.data)
}

https://go.dev/play/p/Cps4Y5mqYFM

Answer 1

As kostix correctly pointed out, in order to modify my tree with that method, I had to pass in a pointer to a pointer to the original tree. Thanks, kostix!

package main

import "fmt"

type node struct {
    data  int
    left  *node
    right *node
}

type root struct {
    root *node
}

func (bt root) addNode(n **node, data int) {
    if *n == nil {
        newNode := node{
            data:  data,
            left:  nil,
            right: nil,
        }
        *n = &newNode
        fmt.Println("Works")
    } else if data < (*n).data {
        bt.addNode(&((*n).left), data)
    } else {
        bt.addNode(&((*n).right), data)
    }
}

func main() {
    tree := root{root: nil}

    tree.addNode(&(tree.root), 6)
    fmt.Println(tree.root.data)
}