code: func DriverErr(err error) (error, bool) {
  	if dbe, ok := err.(*dbErr); ok {
  		return dbe.err, true
  	}
  	return err, false
  }
docs: // DriverErr returns the original error as returned by the database driver
  // if the error comes from the driver, with the second value set to true.
  // Otherwise, it returns err itself with false as second value.