Just had to deal with Go iterators and I can say that they fit the language well.

They're push iterators. It's as if you're just appending items to an array. Actually much easier to explain when you are teaching the language to begginers while not expecting them to use it for much other than surface level utilities.

They compile down to nonlocal returns to try to keep it fast, but of course it's still slower than a state machine, in typical Go fashion

And when you know slightly more than a single lick of programming, the design and implementation of them looks very obviously moronic and catered to beginners.

Some people were arguing that this approach makes it more "functional" but that's very far from the truth. Push iterators are very imperative, pull iterators (Iterator::next, which returns Option<T>) are actual functional, correct and fast way to do it.