Bound your waits

Use a timeout when your program needs control back even if no message arrives. Timeouts are u64 milliseconds; zero performs an immediate check.

def main() -> Result[(), IoError | RecvTimeoutError | SendTimeoutError[i64] | AllocError]:
    sender, receiver = channel[i64](1)?
    match receiver.recv_timeout_ms(0):
        case Ok(value):
            print(value)?
        case Err(RecvTimeoutError.TimedOut):
            print("nothing yet")?
        case Err(RecvTimeoutError.Disconnected):
            print("senders finished")?
    sender.send_timeout_ms(42, 0)?
    print(receiver.recv_timeout_ms(0)?)?
    Ok(())

nothing yet
42

send_timeout_ms(value, milliseconds) returns an unsent value in SendTimeoutError[T].TimedOut(value) or .Disconnected(value). You can retry, store, or drop it. A timeout does not discard the message.

Timeouts limit waiting, not total wall-clock execution. Lock contention and scheduling can delay return. A message already available at the check is received even with a zero budget. To bound several waits by one total budget, share a deadline.