It cannot be a better C. You cannot implement exceptions in it using set jump for example, but the biggest problem is memory management. You can't implement your own arena allocator in golang.
I've drastically sped up commercial shipping C code by implementing arena allocators and Go is my daily driver and it's not clear to me why you're making this claim.
Not the OP but I guess what they are saying is that since this language is a subset of go and if you use it as such then an arena allocator cannot be used in the transliterated code.
Maybe it's possible to force the transliteration to use a different allocator and then you could use the one you wrote in C?