Panic in `UpgradeableConnection` due to `unwrap`

[DDtKey]

Version
1.x.x & current master (203d1b090d0d0349c7e373e881ac4ddba72129be)

Platform
Seems doesn't matter

Description

I encountered a panic for http/1 connection:

panic was raised: panicked at .../src/server/conn/http1.rs:504:56

I.e this line has panicked due to unwrap

hyper/src/server/conn/http1.rs

Line 504 in 203d1b0

match ready!(Pin::new(&mut self.inner.as_mut().unwrap().conn).poll(cx)) {

I wasn't manage to build an MRE yet, but the issue is worth filling out

Btw, it's already second panic due to unwrapping after 1.x release (see #3615). I think the use of unwrap should be given more attention