/// A lock-free Single-Producer-Single-Consumer (SPSC) FIFO channel.
/// A lock-free Multi-Producer-Single-Consumer (MPSC) FIFO channel.
/// A lock-free Single-Producer-Multi-Consumer (SPMC) FIFO channel.
/// A lock-free Multi-Producer-Multi-Consumer (MPMC) FIFO channel.
/// The error of `Sender::send` operation. Occurs if all receivers were
/// disconnected.
/// The error of `Receiver::recv` operation.