Exactly - if you have Xs that are foolike, and Xs that are barlike, the perhaps you should have Yz and Zs instead.

Further, if you want to validate that your X is barlike, all you have to do now is make sure you have some function f : Y -> Z. If you want to scrutinize your validation logic, then you need only look at all functions of that specific type in your program.

Admittedly, go is probably not a language with the best support for these kinds of constructs.