Ways to modify a result of a more high-level resolver

I have something like this in my schema
```
type Query {
request: QueryMessageOt!
}

type QueryMessageOt {
requestID: ID!

offline: Boolean!

executionTime: Float

cargo(filter: CargoFilterIt!, cursor: String, limit: Int): CargoResult
}
```

How can i modify root fields in my `cargo` resolver? For example, i want to accumulate the execution time, but when i do this:
```go
func (r *queryMessageOtResolver) Cargo(ctx context.Context, obj *model.QueryMessageOt, filter model.CargoFilterIt, cursor *string, limit *int) (*model.CargoResult, error) {
*obj.ExecutionTime += 777.0
return nil, nil
}
```
i still get old execution time from `request` resolver.