[hannibalhorn]

It's important to compare with the previous slide, to see the problem this is trying to solve. It'd be really easy to do a lot of

  if err != nil {
    http.Error(w, err.Error(), http.StatusInternalServerError)
    return
  }

all over the place, as the error return type isn't part of the standard Handler signature.

The decorator approach lets you return errors from your handlers, and then have your actual error handling centralized; you may want to send an e-mail to the ops team, send it to a third party exception management web service, etc.