[Kamq]

I think more idiomatic go for the first case would be:

    getNext := iterableThing.Iterator()
    for next, ok := getNext(); ok; next, ok = getNext() {
        ...
    }

Which, yeah, the range cleans it up a bit, but it's not doing quite as much work as you're implying.

[davenoul]

Don't forget that the important bit in Go is readability of the code. To me the range form is much easier to reason about than this for loop.

[Kamq]

If we're going for readability instead of trying to stick to the case presented above, I'd go with:

    for i.HasNext() {
        current := i.GetNext()
        ...
    }

And just mutate the internal state of the struct. Probably throw it behind some sort of interface like:

    type Iterator[T any] interface { // feel free to strip out the generic
        HasNext() bool               // if you really only have one type
        GetNext() T                  // you do this with
    }

I think this still loses to ranging over a function, but I still think it should be compared to what you can do with the current language as opposed to what was originally posted.