Hi, I am the author of gopher-os. It started as a fun research project to learn more about the Go runtime internals and I didn't really expect it making it to HN.
If you take a look at the Go runtime sources you will notice that all the low-level arch/os-related bits have been split into separate files which usually invoke some syscalls (e.g. the memory allocator eventually calls mmap)
The idea I am currently investigating is to first provide an implementation for things such as physical memory allocation and virtual memory mapping which would ultimately allow me to bootstrap the Go allocator. From that point onwards the plan is to incrementally add more features and gradually initialize the rest of the runtime.
This is much more difficult than it sounds as all code must be written in such a way to prevent the compiler from calling the runtime allocator (no variables allowed to escape to the heap).
You can find the source code here: https://github.com/achilleasa/gopher-os