Delphi REST request async cannot populate TList

Question

I have declared these new types:

type
 TRacer = record
  name: string;
  win, tie, loss, points: integer;
 end;

 TRacersList = TList<TRacer>;

I have a procedure in a datamodule that looks like this:

procedure DMConnection.getDivision(aList: TRacersList; const game, id: string);
begin

 //1) setup the REST params
 RESTRequest.Params[0].Value := game;
 RESTRequest.Params[1].Value := id;

 //2) execute async so UI won't freeze
 RESTRequest.ExecuteAsync(procedure
 var tmp: TRacer;
    ja: TJSONArray;
    jv: TJSONValue;
 begin

  //parse the JSON. The RESTResponse is a TRESTResponse that holds the result of the RESTRequest. I have made a test inside the component (right click -> execute) and it works properly (= I can see the JSON inside the Content property).
  ja := TJSONObject.ParseJSONValue(RESTResponse.Content) as TJSONArray;

  for jv in ja do begin
   tmp.name := jv.GetValue<string>('name');
   tmp.win := jv.GetValue<integer>('Wins');
   tmp.tie := jv.GetValue<integer>('Ties');
   tmp.loss := jv.GetValue<integer>('Loss');
   tmp.points := jv.GetValue<integer>('Pts');

   aList.Add(tmp);
  end;

 end);

end;

If you are wondering, this is the JSON string:

[{"name":"payer1","Wins":"1","Ties":"0","Loss":"0","Pts":"3"},{"name":"Velocity","Wins":"0","Ties":"0","Loss":"1","Pts":"0"},{"name":"test2","Wins":"0","Ties":"0","Loss":"0","Pts":"0"}]

In the main form I am able to call the procedure in this way:

DMConnection.getDivision(myList, 'mku', 'k2');

---

I have the following problem. The variable myList: TRacersList is created and freed in the OnCreate and OnDestroy events of the form. If you try to run this code:

DMConnection.getDivision(myList, 'mku', 'k2');
ShowMessage(myList.Count.toString);

The result is 0. Instead, if I put the aList.Add(tmp); OUTSIDE the async request (for example, before the parameters setup) the count is 1.

This means that the list is being filled when it's outside the completion handler of the ExecuteAsync but when the list is inside it doesn't. Any idea?

I have cheched that by default the Synchronize is set to True, so adding

TTHread.Synchronize(nil, procedure
begin
 aList.Add(tmp);
end)

Would be useless. What should I do? I'd like to have this parsing/rest stuff in the datamodule so I can keep the internet stuff separated from my app implementation.