Another possible extension of that design is using error types for HTTP codes. Something like:

  type HTTPError struct {
          Err  error
          Code int
  }

And then, with a couple of wrappers like this:

  func errorNotFound(err error) (wrapped error) {
          return &HTTPError{
                  Err:  err,
                  Code: http.StatusNotFound,
          }
  }

you could do something like this:

  return errorNotFound(err)

or this:

  return errorInternal(err) // 500 Internal Server Error