Depends a bit what you want out of it. C for fundamentals, Go for fast web serving, Rust for stuff that's memory safe?
I might make some kind of machine learning application in it later down the line though.
Also if you're mucking about with machine learning a lot of the libraries seem to be in C or C++. I played about a bit with computer vision using Python but sometimes the Python bindings don't work or don't exist and I was thinking it would be easier to just call the things from the C/C++ they are written in.