diff --git a/codes/go/chapter_tree/binary_search_tree_test.go b/codes/go/chapter_tree/binary_search_tree_test.go
index 45d59bd..955ebdb 100644
--- a/codes/go/chapter_tree/binary_search_tree_test.go
+++ b/codes/go/chapter_tree/binary_search_tree_test.go
@@ -7,7 +7,7 @@ package chapter_tree
 import "testing"
 
 func TestBinarySearchTree(t *testing.T) {
-	nums := []int{8, 9, 10, 11, 12, 13, 14, 15, 1, 2, 3, 4, 5, 6, 7}
+	nums := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}
 	bst := NewBinarySearchTree(nums)
 	t.Log("初始化的二叉树为: ")
 	bst.Print()
@@ -32,9 +32,6 @@ func TestBinarySearchTree(t *testing.T) {
 	bst.Remove(1)
 	t.Log("删除结点 1 后的二叉树为: ")
 	bst.Print()
-	bst.Remove(12)
-	t.Log("删除结点 12 后的二叉树为: ")
-	bst.Print()
 	bst.Remove(2)
 	t.Log("删除结点 2 后的二叉树为: ")
 	bst.Print()
diff --git a/codes/go/pkg/tree_node.go b/codes/go/pkg/tree_node.go
index 6175688..b62dc60 100644
--- a/codes/go/pkg/tree_node.go
+++ b/codes/go/pkg/tree_node.go
@@ -9,9 +9,6 @@ import (
 	"fmt"
 )
 
-// nodeNotExist represents node don't exist.
-const nodeNotExist int = -1
-
 type TreeNode struct {
 	Val   int
 	Left  *TreeNode
@@ -54,11 +51,11 @@ func ArrayToTree(arr []int) *TreeNode {
 }
 
 // TreeToArray Serialize a binary tree to a list
-func TreeToArray(root *TreeNode) []int {
+func TreeToArray(root *TreeNode) []any {
 	if root == nil {
-		return []int{}
+		return []any{}
 	}
-	arr := make([]int, 0)
+	arr := make([]any, 0)
 	queue := list.New()
 	queue.PushBack(root)
 	for queue.Len() > 0 {
@@ -68,7 +65,8 @@ func TreeToArray(root *TreeNode) []int {
 			queue.PushBack(node.Left)
 			queue.PushBack(node.Right)
 		} else {
-			arr = append(arr, nodeNotExist)
+			// node don't exist.
+			arr = append(arr, nil)
 		}
 	}
 	return arr