Consider changing Task.Poll interface function to add a context.Context argument

[inkel]

While looking at the current interface definition for Task I've seen that Task.Poll doesn't accept any argument nor return an error (more on this later).

Then looking at implementations of the interface, I've found that a context could be useful here:

• CallbackTask creates a context.Background(), thus not giving the option to pass a root context that could be cancelled for different reasons.
• ShellTask could instead create the command using exec.CommandContext so we could have finer control over the executed binary.
• NestedTask could pass the context to its children.

Contexts are great and very powerful when used this way. As an example, if the interface was called this way, we could have in our main.go the following piece of code:

func main() {
	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
	defer stop()

	// …create tasks and everything…

	root.Poll(ctx)

	// …continue…
}

And if the user clicks ^C while the program is calling root.Poll it will cancel the context, thus passing this cancellation information down to all processes and we will have better resource management and cancellation, rather than an abrupt termination.

What do you think?

PS: I mention this function also returning an error. I think it could be very useful information to have, for instance, implementations would perhaps return ctx.Err() which might indicate to the caller that the context was cancelled or timed out.