I had to pick something i was familiar with too. We need this on a shorter timeframe (when is that not true? haha), and evaluating a language is hard.
As it is, this was a partial reason against Rust for me. After my time learning Rust, i'm still not 100% confident in my ability on it. My lack of experience and thusly productivity-hit is a real factor i had to calculate. Moreso with the rest of the team.
With Scala/etc i would be learning it new myself, and it was a gamble i wasn't going to take. Especially because our application is not intensive to specific problems that some languages excel in (concurrency, etc).
I'm sticking my neck out choosing a language, so i wanted to be quite sure i make the right choice for us. Well, as best i can - i am new in this shop after all.. i hope i made the right one :)
Honestly, unless you need some special library or your team is already familiar with those languages, I would pretty much always recommend Go over those languages. Everything is just simpler, and it's at least as fast as any of those languages.
