style(go): fix go code style

Make the classes and methods in the package private, in case misuse

codes/go/pkg/print_utils.go

@@ -76,7 +76,7 @@ func printTreeHelper(root *TreeNode, prev *trunk, isLeft bool) {
 	printTreeHelper(root.Left, trunk, false)
 }
 
-// trunk Help to Print tree structure
+// trunk Help to print tree structure
 type trunk struct {
 	prev *trunk
 	str  string
@@ -103,4 +103,4 @@ func PrintMap[K comparable, V any](m map[K]V) {
 	for key, value := range m {
 		fmt.Println(key, "->", value)
 	}
-}
+}