Function rustls_default 

pub fn rustls_default<B>() -> Client<RustlsConnector<HttpConnector>, B>
where
    B: HttpBody + Send,
    B::Data: Send,

Available on (crate features http1 or http2) and crate feature rustls only.

With the default hyper_rustls::HttpsConnector.

The config is determined as follows. I think the cert root is similar to the reqwest crate.

1. Cert roots

• if the feature rustls-webpki-roots is enabled, then use HttpsConnector::with_webpki_roots();
• if rustls-webpki-roots is disabled and rustls-native-roots enabled, then HttpsConnector::with_native_roots();
• otherwise compilation fails.

The feature rustls is equivalent to rustls-webpki-roots.

2. Scheme

HTTPS only

3. HTTP version

• if the feature http1 is enabled, then call HttpsConnector::enable_http1();
• if the feature rustls-http2 is enabled, then call HttpsConnector::enable_http2().

This is not exclusive: if both features are enabled, then both methods are called.