Ruby is an extremely powerful language, with the only drawback of being truly slow. Crystal solves this problem with flying colors by offering almost full Ruby compatibility along with very efficient native code generation.
Unfortunately it's still young and lacks user base as well as ports to other architectures.
In a discussion involving C, C++, Rust and Nim, "on par with Go" is probably not considered fast. Also, it would seem Crystal is closer to those languages I mentioned than to Go in speed.
Ruby is an extremely powerful language, with the only drawback of being truly slow. Crystal solves this problem with flying colors by offering almost full Ruby compatibility along with very efficient native code generation. Unfortunately it's still young and lacks user base as well as ports to other architectures.