code: func (c *conn) CheckNamedValue(nv *driver.NamedValue) error {
  	switch nv.Value.(type) {
  	case Lob, *Lob:
  		nv.Value = nil
  	}
  	return nil
  }
docs: // CheckNamedValue implements NamedValueChecker interface.
  // implemented for conn:
  // if querier or execer is called, sql checks parameters before
  // in case of parameters the method can be 'skipped' and force the prepare path
  // --> guarantee that a valid driver value is returned
  // --> if not implemented, Lob need to have a pseudo Value method to return a valid driver value