CREATE TYPE trow AS (id numeric);

CREATE OR REPLACE FUNCTION fnc_etl(curvData refcursor)
 RETURNS SETOF trow
 LANGUAGE plpgsql
AS $function$
declare
  vResult trow;
begin 
  loop
    fetch curvData into vResult;
    exit when not found;
    return next (vResult);
  end loop;
  close curvData;
end;
$function$;

Select * from fnc_etl(fnc_getcursor(...));