I use Scala at work. I would rather write in Go than in Scala. While there are many things to like in Scala there are also many misfeatures such as the `implicit` key word which can create a lot of spooky action at a distance. Scala is an engineering tour de force and has many interesting ideas. However, I find that it has too many features and has a syntax with encourages obscure code. In contrast Go may be verbose at times but it is always very easy for me to read and follow.
I recently needed to dive into a legacy Scala code base which had not been worked on in a year. The engineer who had written it had moved on from the company and no one knew how it worked. The code was extremely difficult to read and reason about. Some of this was do to the programmer who wrote it but some of it was also do to language features. Is it possible write clear and concise Scala? Absolutely! But, the language does not necessarily encourage that style at this time.
Other functional languages I have used include: Scheme and SML. I want to check out OCaml next. I have also played around a bit with F* (not F#).
