I've been playing with more complex languages like Rust and Pony (neither really functional, but with advanced type systems) and have to say writing some Go mor

I've been playing with more complex languages like Rust and Pony (neither really functional, but with advanced type systems) and have to say writing some Go more recently has been a pleasure :D But it really is a trade off between whether you need to prioritize correctness or development speed. Regarding your comment that Go maybe took it a bit too far: I agree... in the functional world, I found a language that I really enjoyed and that maybe fixes more FP problems: Elm! Quite easy to read and write Elm code, it's a shame that it only exists on the front-end (it compiles to browser JS), would be really cool if someone ported it to the backend as well.