Well, I hoped to use Go to avoid both:

a) writing in C for performance (and having to setup glib et al to make it comfortable)

and:

b) carrying the JVM with me to run something.

(And, no, I won't consider AOT compilers for Java. I want to deal with reasonably mature and widespread technologies and tooling).

So, there are my constraints. Given those, maybe C++ is the ticket. D is not mainstream enough, and Rust I've played with and I like very much but is still in flux.