annotate errors

[Stebalien]

See: libp2p/go-libp2p-kad-dht#221

[anacrolix]

I recommend using https://godoc.org/github.com/pkg/errors#Wrap instead.

[Stebalien]

@anacrolix maybe... It looks like that package records a stack trace. Generating stack traces for errors can get a bit expensive. We'd have to carefully profile that before using it.

Ideally, it would provide an option to disable collecting stacks. I wonder if they'll accept a PR.

[anacrolix]

The errors.WithMessage function handles that.

[Stebalien]

I see. However, it still adds stack traces by default everywhere else. If we're going to pick a third-party errors library (we should, IMO), I'd like to use it everywhere for. Otherwise, nice features like Cause aren't very useful.