context

type Callback interface {
	// OnCancelled is called when the context is cancelled.
	OnCancelled(status.Status)
}

type CancelContext interface {
	Context

	// Cancel cancels the context.
	Cancel()
}

type Context interface {
	// Done returns true if the context is cancelled.
	Done() bool

	// Wait returns a channel which is closed when the context is cancelled.
	Wait() <-chan struct{}

	// Status returns a cancellation status or OK.
	Status() status.Status

	// AddCallback adds a callback.
	AddCallback(c Callback)

	// RemoveCallback removes a callback.
	RemoveCallback(c Callback)

	// Free cancels and releases the context.
	Free()
}