They automatically translated C code to Go code. The objective was to produce correct Go code, speed was not an immediate concern - the auto-translated code mostly is very bad Go code, speed wise. Optimizing the Go code base of the compiler is the next step, planned to happen in subsequent releases.
Generally, compilers aren't very good at compiling code that isn't idiomatic for the language. This is by design, since compiler writers try to make idiomatic, common code fast first and foremost.
Comments
They automatically translated C code to Go code. The objective was to produce correct Go code, speed was not an immediate concern - the auto-translated code mostly is very bad Go code, speed wise. Optimizing the Go code base of the compiler is the next step, planned to happen in subsequent releases.
Is it? It might not be particularly optimized, but why would that ("very bad speed wise") be the case?
Generally, compilers aren't very good at compiling code that isn't idiomatic for the language. This is by design, since compiler writers try to make idiomatic, common code fast first and foremost.