Personally i prefer go, but these are pretty standard languages; so learning the in's and out's really isn't all that time consuming (you aren't going to have to change how you think about programming like say rego). Since you have python experience these should be no big deal, but maybe worth playing with a bit if you are trying to get a job in either language and need to cross off that bullet.

As for expanding your learning, i'd try something like functional programming (haskell), or query language like rego above. Neither of these will be great for your resume though.