Ability to shutdown server with error

[Ryan]

Feature Request

A common pattern is to run background tasks (goroutines) from an init server function (e.g. a controller). When these background tasks fail, (consider the case where due to a programmer bug there is a panic)

It would be nice to write an init func something like

func main() {
    err := startServer()
    if err != nil {
        os.Exit(1)
    }
    os.Exit(0)
}

func startServer() error {
	return witchcraft.NewServer().
		WithInitFunc(initFunc).
		Start()
}

func initFunc(ctx context.Context, info witchcraft.InitInfo) (cleanup func(), rErr error) {
	go func() {
        err := doBackgroundTask(ctx)

        // ... log / handle error

		if err != nil{
			err := info.ShutdownServerWithError(ctx, err)

            // ... handle err

		} else {
            info.ShutdownServer(ctx)
        }
	}()
	return nil, doRun(ctx,conf)
}

And have server.Start() actually return an error as desired.

Strawman proposal would be to add a new method to InitInfo:

	// ShutdownServerWithErr closes the server, waiting for any in-flight requests to finish (or the context to be cancelled).
	// The server is shutdown with an error, causing `Start` to return an error.
	ShutdownServer func(context.Context, err error) error

I'd be happy to implement this if this sounds good.

[Nick Miyake]

Thanks for the feedback. Just for clarification, is it the case that the current Close() and Shutdown(context.Context) functions do close/shut down the server, but cause the start function to just return nil rather than an error?

[Ryan]

Yup, exactly

[Nick Miyake]

Got it. Yes, I think this is reasonable -- would just say that, in the comment/documentation for the function, you should note that the function is the equivalent of calling Shutdown, but will return a non-nil error. I think it would also make sense for the PR to update the implementation of Shutdown to use ShutdownServer with a nil error.