Sort and distinct in mongoose

My mongoose query is:

Spread.find(findCase).where('loc').near({
        center: {
            type: 'Point',
            coordinates: [self.lon, self.lat]
        },
        maxDistance: distance
}).sort({ts : -1}).distinct("postId").exec();

So I get the error:

Error: sort cannot be used with distinct

But if I pass the query with console

db.spreads.distinct({}).sort({ts: -1});

That is ok.

So why mongoose doesn't let me to select distinct and sort in one query and how can I do it?

From the docs, sort cannot be used with distinct.

Cannot be used with distinct()

But you can perform an aggregation operation:

Spread.aggregate(
{$geoNear:{
  "near":{"type":"Point","coordinates":[self.lon, self.lat]},
  "distanceField":"dist.calculated",
  "maxDistance":distance,
  "query":findcase,
  "spherical": true
}},
{$sort:{"ts":-1}},
{$group:{"_id":"$postId"}},function(err,resp){
  console.log(resp);
  // handle response.
}
)

Note: A 2dsphere Index needs to exist on the collection over the loc field. To create an Index, refer: Does applying a 2dsphere index on a mongoose schema force the location field to be required?.