I want to learn new language because I want to learn new ways of thinking about problems and new ways of solving problems. I want to improve myself at programming. I can't feel like I'm programming or solving problems at web development anymore. I'm just doing same things at web development.
C/C++ is good option but it has lots of keyword (over 90 if I remember correctly) and it's old.
Rust is good option too. New and modern language, Mozilla develops it (I love Mozilla) and it's really favorite language at stackoverflow but it's new and doesn't have much library bla bla.
Python is good option. It has lot's of library, very well supported...
What would you do and why?