Didn't find it in the readme: does anyone know what general "level" of microcontrollers are the project author(s) hoping to target? I suppose that because of the Go spec already, the minimum required architecture must be at least 32bit?
All backends supported by LLVM should be fairly easily supported by TinyGo. In fact, I've had the blinky example running on an Arduino a while back (8-bit, 2kB RAM, 32kB flash). There is nothing in the Go spec that requires a 32-bit system, just like there is nothing in the C standard that requires a 16-bit system (ints are at least 16 bits).
The biggest obstacle is not the fact that it is 8-bit, but the fact that it is a Harvard-style processor with a separate address space for code and data. I've added a section to the README to explain this. Also, garbage collection is going to be painful.
Maybe "and more" means there's hope for Go style garbage collection.