I understand there's a much more limited subset of developers for Rust or even Go vs. C/C++. Also, I recall hearing about Rust before systemd, but am not sure. Today, it would probably be my first choice. Not that go is a bad choice, I just don't think it's a good spot for it. I also agree that either are probably quite a bit better than C/C++ options.
I'm not against go, other than gc and some size considerations. Given that a lot of k8s infrastructure for the likes of CoreOS and similar are written in it, it's definitely not a bad option. I think that today, and more so in late summer as async/await syntax settles, that Rust should be a first consideration for any low-level system code.
Rust might be better now; my primary concern would be community size and whether I was limiting my contributor base, which Go also has as a concern. In both cases though I'd take it over C/C++ being used on such a critical project at this juncture.
In 2010, though... yeah, choices are a lot worse.