Allow for sessions to be shared between subdomains.

[Kugyan]

I'd like to make a login system, like auth.example.com then the dashboard at dashboard.example.com, but I can't because sessions won't be shared between subdomains.

[joewagner]

As long as the cookie value makes it the this middleware, you should be able to accomplish what you're hoping. If you're having a problem, feel free to open a PR or elaborate on where you are getting stuck.