replace Go with Python in the text, and you won't see a difference: there are iterable, keyable, file-like interfaces, etc. And creating your own is trivial.
With all the cases were Go pushes you to use interface{} that's the case in Go a lot of the time too.
However, you can wrap an interface{} using container (for example), with type-specific input and output functions, getting back compile-time type-checking. Yes, it is not optimal, and yes, you're still paying the price for type assertions.
If it had Generics that would be another thing.
I would like to see a good solution for this that integrates well with the rest of the language.
I would like to see a ho-hum solution for this that's on par with what's offered on other languages.
I say that because the Go designers, despite having designed a quite mediocre language, suddenly when it comes to generics the want the perfect no-compromises solution or nothing.
What people like about Go is its mix of features, not some specific one by itself.