`reqwest::Client::default()` doesn't work with reqwest-websocket if ALPN is available

[rinsuki]

currently we are not supporting WebSockets over HTTP/2, but not restricting HTTP request to HTTP/1.1.

as a result, if user using reqwest with ALPN supported backends (e.g. native-tls-alpn or rustls series), reqwest-websocket will not work with default client.

We should restrict it with .version(reqwest::Version::HTTP_11) (RequestBuilder), but actually this is broken now (ref. seanmonstar/reqwest#2116 )

so I think we can take those workarounds for now:

• more detailed HandshakeFailed error (probably you also want to check HTTP version?)
• forced to use HTTP/1.x series by reqwest::Client::builder().http1_only().build() in example codes

[jgraef]

Thanks for opening the issue!

I looked into implementing the handshake for HTTP 2, but if we don't even know if the request will be HTTP 1 or 2, this is impossible. For now I made the handshake error more detailed. I'm not sure yet if I want to change the examples, because it makes them even more verbose.