message: Client Close
  Summary: - adding the ability for the client echo sample to close the socket thru a `/close` command
diff: @@ -233,6 +233,7 @@ class EchoClient : public quic::QuicSocket::ConnectionSetupCallback,
  startDone_.wait();
  std::string message;
  + bool closed = false;
  auto client = quicClient_;
  if (enableStreamGroups_) {
  @@ -246,6 +247,12 @@ class EchoClient : public quic::QuicSocket::ConnectionSetupCallback,
  }
  auto sendMessageInStream = [&]() {
  + if (message == "/close") {
  + quicClient_->close(folly::none);
  + closed = true;
  + return;
  + }
  +
  // create new stream for each message
  auto streamId = client->createBidirectionalStream().value();
  client->setReadCallback(streamId, this);
  @@ -265,7 +272,7 @@ class EchoClient : public quic::QuicSocket::ConnectionSetupCallback,
  };
  // loop until Ctrl+D
  - while (std::getline(std::cin, message)) {
  + while (!closed && std::getline(std::cin, message)) {
  if (message.empty()) {
  continue;
  }
  