> and that carries a MAJOR limitation, because the instance of ImplementsFooer (f) inside your function is a copy of the object you called it on. That means you cannot manipulate data-members in interface-functions, even inside your own struct.<p>You can, by doing it like this: <a href="https://play.golang.org/p/5yXfOf6Y_3" rel="nofollow">https://play.golang.org/p/5yXfOf6Y_3</a><p>EDIT: I'll just file an issue as I doubt the OP is the author.