Function capnp_futures::serialize::try_read_message

pub async fn try_read_message<R>(
    reader: R, 
    options: ReaderOptions
) -> Result<Option<Reader<OwnedSegments>>> where
    R: AsyncRead + Unpin, 

Begins an asynchronous read of a message from reader. Returns None if reader has zero bytes left (i.e. is at end-of-file). To read a stream containing an unknown number of messages, you could call this function repeatedly until it returns None.