  explicit AlpnClient(AsyncSSLSocket::UniquePtr socket)
      : nextProto(nullptr), nextProtoLength(0), socket_(std::move(socket)) {
    socket_->sslConn(this);
  }
  explicit AlpnClient(AsyncSSLSocket::UniquePtr socket)
      : nextProto(nullptr), nextProtoLength(0), socket_(std::move(socket)) {
    socket_->sslConn(this);
  }