For example the C++ templates rules are themselves a turing-complete language.
If by generics you meant some really basic features, I think you can do pretty well with interfaces. They're already in the language.
If by generics you meant the full-package, i think you could end up with something pretty complex all the time.
Most generic implementations are not Turing-complete, and looking at C++, this doesn't sound like a particularly tempting proposition.
And while I'm not particularly familiar with Go, I don't see how you can get a feature set equivalent to a simple implementation like Java's out of Go interfaces ("you can just cast" is not a good answer).