Function accept_hdr_async 

pub async fn accept_hdr_async<S, T, C>(
    stream: T,
    callback: C,
) -> Result<WebSocketStream<S>, Error>
where
    S: Splittable + 'static,
    T: IntoMaybeTlsStream<S>,
    C: Callback + Unpin,
    <S as Splittable>::ReadHalf: AsyncRead + Unpin,
    <S as Splittable>::WriteHalf: AsyncWrite + Unpin,

Available on crate feature ws only.

Accepts a new WebSocket connection with the provided stream.

This function does the same as accept_async() but accepts an extra callback for header processing. The callback receives headers of the incoming requests and is able to add extra headers to the reply.