[bitexploder]

They probably mean you can use interface{} and create a typing black hole if you really wanted to. Otherwise, I don't know.

[kuschku]

Or maybe they mean that you HAVE to use interface{} for any reasonable kind of generics, such as developing generic data structures, or generic handlers for RPC interfaces allowing arbitrary nesting?

Even the stdlib uses interface{} everywhere now: https://tip.golang.org/pkg/sort/#Slice

[bitexploder]

Is a good point. Smells of void pointers and old school Java collections.