TcpStream::connect timeout settings

[ragona]

Hi there,

I read through some of the other issues on timers in romio, but it seemed slightly different than changing the underlying mio/net2 settings. I want to open a large number of TCP connections to different hosts, which may or may not respond. In order to prevent an excessive number of open files on the client I want to configure aggressive connection timeouts to prune connections that don't respond quickly.

I'd be happy to try to submit a PR to add a Builder object or something to make TcpStream more configurable, but I'm not sure if there is somewhere I should be looking for an example of this. (I'm digging into the Rust async/await story, and I'm not experienced in it yet.)

Here's a brief snippet that shows the code I'm using -- I appear to be hanging onto connections that fail for some time, and if there is an alternate path to fix I'd be happy to try that out instead.

fn main() -> io::Result<()> {
    let delay = 1e9 as u64 / REQUESTS_PER_SECOND;

    executor::block_on(async {

        for _ in 0..TOTAL_REQUESTS {
            juliex::spawn(async move {
                let addr = random_addr(80);
                match TcpStream::connect(addr).await {
                    Ok(mut stream) => {
                        stream.write_all(&REQUEST)
                            .await
                            .expect("Failed to write to socket")

                        stream.close()
                            .await
                            .expect("Failed to close socket");

                        println!("Success: {:?}", &addr);
                    }
                    Err(e) => {
                        eprintln!("Failed to connect: '{}'", e);
                    }
                }

            });
        }
    });

    Ok(())
}

Thanks! Ryan