Almost forgot: in Go, classes aren't "closed". While you cannot "monkey patch" and change existing methods, you can define new functions, such as my_set_compar

Almost forgot: in Go, classes aren't "closed". While you cannot "monkey patch" and change existing methods, you can define new functions, such as my_set_comparator, that accept each given type as "this". You would then make a new interface, such as my_set_element, which defines method my_set_comparator, and any data types for which you had defined my_set_comparator would automagically meet the new interface.