Fix unclean TLS shutdown (#3191)

* Fix dirty shutdown

* generic comment

Author: levkk

sqlx-core/src/net/tls/tls_rustls.rs

@@ -71,7 +71,13 @@ impl<S: Socket> Socket for RustlsSocket<S> {
         }
 
         futures_util::ready!(self.poll_complete_io(cx))?;
-        self.inner.socket.poll_shutdown(cx)
+
+        // Server can close socket as soon as it receives the connection shutdown request.
+        // We shouldn't expect it to stick around for the TLS session to close cleanly.
+        // https://security.stackexchange.com/a/82034
+        let _ = futures_util::ready!(self.inner.socket.poll_shutdown(cx));
+
+        Poll::Ready(Ok(()))
     }
 }