Match any Connection header that contains the Upgrade token for websocke...

...ts
Only thing I can find is buried in go.net/websocket/hybi.go as part of ReadHandshake

https://code.google.com/p/go/source/browse/websocket/hybi.go?repo=net#471

which would require creating a hybiServerHandshaker which seems websocket impl specific so not sure we should really be calling that here.  I also dont love the check being used in that as it only checks that the string contains "upgrade" which is not as accurate as checking for upgrade as a single token (like the regex is doing)