promise

type Promise interface {
	// Returns whether this promise is complete yet, without blocking.
	IsComplete() bool

	// Returns whether this promise completed with errors, without blocking.
	IsError() bool

	// Unblock all goroutines awaiting promise completion.
	Complete(errors []error)

	// Blocks the caller until the promise is marked complete. This function
	// is equivalent to invoking AwaitUntil() with a zero-length duration.
	// To avoid blocking the caller indefinitely, use AwaitUntil() with a
	// non-zero duration instead.
	Await() []error

	// Blocks the caller until the promise is marked complete, or the supplied
	// duration has elapsed. If the promise has not been completed before the
	// await times out, this function returns with nonempty errors. If the
	// supplied duration has zero length, this await will never time out.
	AwaitUntil(timeout time.Duration) []error

	// Invokes the supplied function after this promise completes. This function
	// is equivalent to invoking AndThenUntil() with a zero-length duration.
	// To avoid blocking a goroutine indefinitely, use AndThenUntil() with a
	// non-zero duration instead.
	AndThen(f func([]error))

	// Invokes the supplied function after this promise completes or times out
	// after the supplied duration. If the supplied duration has zero length,
	// the deferred execution will never time out.
	AndThenUntil(timeout time.Duration, f func([]error))
}

type RendezVous interface {
	// Returns whether this rendez-vous is complete yet, without blocking.
	IsComplete() bool

	// Complete process A's half of the rendez-vous, and block until process
	// B has done the same.
	A()

	// Complete process B's half of the rendez-vous, and block until process
	// A has done the same.
	B()
}