// These switches continue until a call to coroexit(c),
// which ends the use of the coro by releasing the blocked
// goroutine in c and exiting the current goroutine.
//
// Coros are heap allocated and garbage collected, so that user code
// can hold a pointer to a coro without causing potential dangling
// pointer errors.
type coro struct {
	gp guintptr
	f  func(*coro)