LISP append lists function

(defun my-append(list1 list2)
       ( if (null list1) list2 (cons (car list1) (my-append (cdr list1) list2)) )
)

Test Cases

> my-append '() '(a) = (a)
> my-append '(a b c) '(d e f) = (a b c d e f)