Just my opinion (given my own experience and goals; if your experience/goals are different the below may be irrelevant):
As a constant waverer, my answer to the "Go or Rust" question was, after much time, "no".
Instead I'm returning to C++ and trying to learn how to use modern C++ idioms and finding this very productive.
It's a bit frustrating, as C++ is a bloated mess of a language with way too many dark corners, but good discipline can allow you to use a version of it that is really nice. As someone who learned C++ in 1992 (when much of the language wasn't even really there yet) and has only fitfully engaged with good C++ practices over the years, the payoff from learning new parts of C++ has been really much better than a new language.
Plus, neither Rust nor Go are particularly mind-expanding if you're a native C++ speaker (as compared to Python, Prolog, Forth, assembly, Haskell, Lisp, ...).