We wrote a (brief) blog post about this decision way back in 2015 that you might be interested in: https://www.cockroachlabs.com/blog/why-go-was-the-right-choi...

We're generally pretty happy with our choice to use Go for the database, even when it causes us pain like the kind you see in this post. Rust wasn't really ready when we started working on CockroachDB, and we think that we wouldn't have been able to make progress as quickly as we did if we had used C(++).