Header "connection: close" disconnects the client before Response Stream is started

[dkalinowski]

Describe the bug

In our project we use Drogon for HTTP response streaming.
However, when client includes connection header that is not keep-alive, response stream is immediaitely closed.

Source code:

drogon/lib/src/HttpServer.cc

Lines 981 to 990 in cbf63f8

	if (!respImplPtr->ifCloseConnection())
	{
	asyncStreamCallback(
	std::make_unique<ResponseStream>(conn->sendAsyncStream(
	respImplPtr->asyncStreamKickoffDisabled())));
	}
	else
	{
	LOG_INFO << "Chunking Set CloseConnection !!!";
	}

It is common practice to use connection: close to indicate that connection should be closed after processing is finished*, meaning - after HTTP response stream is done.

In our setup, we needed to patch drogon like this: openvinotoolkit/model_server@8ca2918

To Reproduce
Steps to reproduce the behavior:

1. Start drogon with streaming response endpoint defined
2. Request with any client including header connection: close
3. Request is immediately rejected

Expected behavior
Connection is closed after response streaming is finished.

Desktop (please complete the following information):

• OS: ubuntu, redhat, windows
• Client: any

More context
We are using Continue VSCode plugin as a client for code completions: https://github.com/continuedev/continue
We use drogon to serve http streaming (code completions), however, this plugin (client) sends connection: close header.