code: func (elt ZeroIsNullMeddler) PreRead(fieldAddr interface{}) (scanTarget interface{}, err error) {
  	// create a pointer to this element
  	// the database driver will set it to nil if the column value is null
  	return reflect.New(reflect.TypeOf(fieldAddr)).Interface(), nil
  }
docs: // PreRead is called before a Scan operation for fields that have the ZeroIsNullMeddler