Go doesn't need to transition to the kernel to switch threads, does it? It just saves and loads the register state in userland.

IIUC it can, sometimes, avoid a kernel transition when it knows it can schedule the recipient of a message, but I believe that golang creates a threadpool for running goroutines on platforms that use thread primitives.

From https://github.com/golang/go/blob/c7d6c6000a84b61ac8bb2e38e8... I believe "worker threads" are OS threads.