No, it will help with lack of REPL but not with long compilation times. Long compilation times are bad across the board. Go advertises "fast compilation" as one of its key features for a reason.

EDIT: Not to mention, if you write your code as a lot of tiny functions you could just as well write it in C. Once you go for classes and templates, that's where C++ power is visible, but that's also where its compile times suck.

Writing unit tests is nowhere near a replacement for a proper REPL.