Function encode_request 

pub async fn encode_request<B, F, E>(
    req: Request<B>,
    stream_id: u64,
    emit: F,
) -> Result<(), StreamEncodeError<E>>
where
    B: Body + Unpin,
    B::Data: Buf,
    B::Error: Error + Send + Sync + 'static,
    F: FnMut(StreamFrame) -> Result<(), E>,