Any language that uses the actor model for concurrency which is basically every language created in the last decade. Elixir, GO, Akka framework for Java and C#, Pony, Dart, Erlang, ELM, SCALA, ...
F# with it's built in actor model, robust OCaml based syntax, great support for functional Akka[.net] actors, simplified concurrency and asynch programming support, and very own ELM implementation is a great contextual answer for anyone who wants to be on the front lines of lightweight non-blocking concurrent & parallel web development in .Net land.