GeoNear with Mongoose This is my mongoose schema - 

var userDestinationSchema = mongoose.Schema({

    uid: String,                
    update_time: Date,          

    location:{                  //&lt;INDEXED as 2d&gt;
        lon: Number,
        lat: Number
    }
});



var userDestinationModel = mongoose.model('userDestinationModel', userDestinationSchema);


How do I query the model for geoNear?

I tried doing this and it ain't working.

userDestinationModel.geoNear([parseInt(req.params.lon,10),parseInt(req.params.lat,10)],
              { maxDistance : 50, spherical : true }, 
              function(err, results, stats) {
                   console.log(results);
                });


maxDistance : 50 

What is the unit? Km?
I can answer the distance part, but I've never used geoNear with Mongoose I'm afraid - a good way to tell if the issue lies in how you are calling things in Mongoose versus the query itself would be to try it on the mongo shell first to verify that it is returning the results you expect there.  

In terms of the distance, for legacy 2d points (which you appear to be using), the $maxdistance is specified in radians - there is a page here which outlines how to use radians with spherical geometry calculations.  If you use GeoJSON instead (which I would recommend), then it is specified in meters (reference).