1. How to manually manage memory more safely with aid from a borrow checker. 2. If you don't already have experience with an ML/Haskell descent language, it will teach you about more powerful static type systems. 3. General low-level programming concepts that you wouldn't know without experience in C/C++.
Whereas Go doesn't really have much to teach you. The community says it themselves: Go is a very simple language. Even if you needed to learn it for a job, onboarding new workers onto a Go project is really easy. So I don't think you'd add much to your resume just by tacking Go onto the list of languages you know. What Go can teach you about:
1) CSP - Communicating Sequential Processes. I believe this is the concurrency model behind goroutines and channels. But you can learn about CSP in other languages.