webSocket(maxFrameSize:shouldUpgrade:onUpgrade:)
Request+WebSocket.swift:6@preconcurrency func webSocket(maxFrameSize: WebSocketMaxFrameSize = .`default`, shouldUpgrade: @escaping ((Request) -> EventLoopFuture<HTTPHeaders?>) = {
$0.eventLoop.makeSucceededFuture([:])
}, onUpgrade: @escaping (Request, WebSocket) -> ()) -> Response