MustReceive will receive from a Receiver or panic if it is closed.

MustSend will send to a ClosingSender or panic if it is closed.

Poll will wait up until the specified Duration for a message to possibly be returned, advancing the Receiver's Cursor upon success.

Receive returns the next message, blocking indefinitely, and advancing the Receiver's Cursor upon completion.

Send sends a message to a ClosingSender.

ErrReceiverClosed is raised when MustReceive is called on a closed Receiver.

ErrSenderClosed is raised when MustSend is called on a closed Sender.