private string checkIfValidHandshakeRequest(WebSocketContext context)
        {
            var headers = context.Headers;
            return !context.IsWebSocketRequest
                   ? "Not WebSocket connection request."
                   : !validateHostHeader(headers["Host"])
                     ? "Invalid Host header."
                     : !validateSecWebSocketKeyHeader(headers["Sec-WebSocket-Key"])
                       ? "Invalid Sec-WebSocket-Key header."
                       : !validateSecWebSocketVersionClientHeader(headers["Sec-WebSocket-Version"])
                         ? "Invalid Sec-WebSocket-Version header."
                         : !validateCookies(context.CookieCollection, _cookies)
                           ? "Invalid Cookies."
                           : null;
        }