use Duration;
use Instant;
use crateCallback;
/// Represents an `Ack` as given back to the caller. Holds the internal `id` as
/// well as the current ack'ed state. Holds data which will be accessible as
/// soon as the ack'ed state is set to true. An `Ack` that didn't get ack'ed
/// won't contain data.
pub
pub type AckId = usize;