I recommend Clojure. It will, along with other lisps and functional languages, completely change the way you think about coding. It has a vibrant community, the author is very active and gives great talks, it’s interoperable with Java, it’s a lisp, and it’s functional. You can also hit swap production code with ease.

It’s a fun language to learn as it has a repl to interactively develop with and it has a fun online, free book to begin with called Clojure for the Brave and True.

The single biggest reason I recommend it, is purely because Code is Data. In other words, you can write code to write code very easily and it’s a super meta concept that is very accessible to beginners.