I (personally) would bet on Elixir, particularly if the team writing it would be learning an alternative like Go anyway.

Go can try to reach parity with Erlang one day...but Elixir already is Erlang...That combined with the fact that Elixir's package management already feels light years ahead of Go's disaster and I think it's a winner. I'm sure I'm wrong and the flames of Go lovers will engulf me in the responses, so take this with a mountain of salt.