Startup sequence should throw if the Startup method isn't void-returning

[GrabYourPitchforks]

We saw a scenario where somebody inadvertently wrote a Task-returning Startup method, and the runtime misbehaved since the method hadn't run to completion before the application was booted.

We should check the signature of the Startup method to make sure it's void-returning before we invoke it.

[Eilon]

Out of curiosity, what should you do if from your Startup method you want to call something that's async? E.g. I want to verify a connection to my database and do some... stuff.

[GrabYourPitchforks]

MyAsyncMethod().Result or MyAsyncMethod().Wait().

[Eilon]

And that's OK? That is, Levi won't flag it in a code review? 😉

[GrabYourPitchforks]

Resolved as 4077c03.