RUSTSEC-2020-0016: net2 crate has been deprecated; use socket2 instead

[github-actions]

net2 crate has been deprecated; use socket2 instead

Details
Status	unmaintained
Package	net2
Version	0.2.35
URL	deprecrated/net2-rs@3350e38
Date	2020-05-01

The net2 crate has been deprecated
and users are encouraged to considered socket2 instead.

See advisory page for additional details.

[neoeinstein]

This one is used by mio v0.6. It looks like tokio 0.3 doesn't require net2, but we still want to support tokio 0.2 while actix is on it. It's not something we have significant control over, though, for the 0.2 users.

[faern]

And we still want to release a patch release of net2 that removes the invalid assumption on the memory layout of std::net::SocketAddr. deprecrated/net2-rs#106. I would like to get this out since I assume a lot of projects will be stuck on tokio 0.2 or even tokio 0.1 for quite a while.