No idea about Go, but I was curious how GPT-4 would handle a request to generate C code, so I asked it to help me write a header-only C string processing library with convenience functions like starts_with(), ends_with(), contains(), etc.) I told it every function must only work with String structs defined as:

struct String { char * text; long size; }

...or pointers to them. I then asked it to write tests for the functions it created. Everything... the functions and the tests... worked beautifully. I am not a professional programmer so I mainly use these LLMs for things other than code generation, but the little I've done has left me quite impressed! (Of course, not being a professional programmer no doubt makes me far easier to impress.)