Callbacks vs Coroutines
TJ Holowaychuk

As i can understand from your post that co is being treated as a coroutine,

so is it that co itself uses a separate call stack or the API’s called by co inside the provided function generator if running on a light weight thread is provided a separate call stack. and if co is doing such task how is it performing the creation of separate call stack, is there any implementation of the later issue done in the the co module?