Slowly migrate to range over func

[petkostas]

I have been struggling to find a good and clean solution for the introduced ordered map structs. Maybe consider and support the range-over-func experiment? It would remove the burden of having to re-create iterators for iterating over elements that are not natively supported by GO libraries 😄 I know it is still experimental, but I hardly find any reasons that this will not become stable in the long term.