docs(websocket): showcase wrapping dns and tcp transport

[melekes]

Closes #3330

[melekes]

Re #3330 (comment) providing Default on the transport, we can do so for tokio, but how to do it for async-io since dns::DnsConfig::system returns future? Is there a async Default trait?

impl Default for WsConfig<T: Transport> {
    #[cfg(feature = "async-io")]
    fn default() -> Self {
        WsConfig {
            transport: dns::DnsConfig::system(
                tcp::async_io::Transport::new(tcp::Config::default()),
            )
            .await
            .unwrap(),
        }
    }

    #[cfg(feature = "tokio")]
    fn default() -> Self {
        WsConfig {
            transport: dns::TokioDnsConfig::system(
                tcp::tokio::Transport::new(tcp::Config::default()),
            )
        }
    }
}

cc @thomaseizinger

[mxinden]

Ready to merge from my end.

Thanks @melekes for making this easier for future users!

Will wait a bit to give @thomaseizinger a chance to reply as well.

[thomaseizinger]

There is no async default so we can't do that unfortunately.

[thomaseizinger]

I would still be in favor of dedicated constructors that take the necessary inner configs:

impl WsConfig {
    async fn new_wss(dns_config: ..., tcp_config: ...) -> Self {}
    fn new_ws(tcp_config: ...) -> Self {}
}

The examples can then move to the docs of these functions.

Happy to merge this too as it is better than what we have today.

Thanks @melekes !

[melekes]

I would still be in favor of dedicated constructors that take the necessary inner configs:

It just feels too cumbersome when I add 4 new methods (2 fn and 2 features: tokio and async-io). I'd be in favor of just merging as is.

[thomaseizinger]

I would still be in favor of dedicated constructors that take the necessary inner configs:

It just feels too cumbersome when I add 4 new methods (2 fn and 2 features: tokio and async-io). I'd be in favor of just merging as is.

Ah yes, I forgot that we'd have to do one per executor.

Approvals have been dismissed because the PR was updated after the send-it label was applied.