code: func NewDateTime2FieldDescriptor(nullable NullableColumn, metadata []byte) (
  	fd FieldDescriptor,
  	remaining []byte,
  	err error) {
  
  	d := &datetime2FieldDescriptor{}
  
  	remaining, err = d.init(
  		mysql_proto.FieldType_DATETIME2,
  		nullable,
  		5,
  		metadata)
  
  	if err != nil {
  		return nil, nil, err
  	}
  
  	return d, remaining, nil
  }
docs: // This returns a field descriptor for FieldType_DATETIME2
  // (i.e., Field_datetimef).  See TIME_from_longlong_datetime_packed (
  // in sql-common/my_time.c) for encoding detail.