Fx v2 wishlist

[abhinav]

Fx v2 is nowhere on the horizon, and is likely never going to happen.
This issue is to track all possible features/issues/changes that we'd want in Fx, should a v2 ever happen.
Part of the purpose here is to start discussion around how, if at all, some of the difficult changes can be accomplished.

Format: Start a new thread for each significant change, discuss within that thread.

[abhinav]

Simplify startup lifecycle

Lifecycles are a frequent point of confusion. The two phase startup (Invoke and OnStart) takes a second for users to get their head around.

One option here would be to delete OnStart hooks completely. Any long-running work will be scheduled from constructors and invoked functions. It's much more obvious to think in terms of "my constructor has to return the thing, so it can't block forever."
Stop hooks would still be a thing, though.

Some questions to consider:

• How would the OnStop hooks API look?
• How would components that do need two phase startup do it? For example, if we have an HTTP server, and handler registration is a separate step from construction, we wouldn't want to start the server until after all handlers are registered. (For the sake of this example, let's assume that moving the handlers into the constructor isn't an option.)

[abhinav]

Delete fx.Printer

fx.Printer is the old means of overriding where Fx event logs were printed.
This has long since replaced by fxevent.Logger and the fx.WithLogger API.