After Groupby，executing Aggregation error

[huotianyu]

After doing a lot of calculations, when it comes to groupby, Aggregation encountered a problem。
in the dataframe，map is not nil，but row is 0,
“
func (gps Groups) Aggregation(typs []AggregationType, colnames []string) DataFrame {
if gps.groups == nil {
return DataFrame{Err: fmt.Errorf("Aggregation: input is nil")}
}
”
Just judging whether “nil” is insufficient
Do you have any good suggestions or Could you fix this problem