[SalesForce] JSON.Serialize method not returning null fields

We are also facing the same problem.

There is some answer from APEX team on this at below link : JSON.Serialize method not returning null fields

But it looks like that question is still open.

You need to represent each inner object of the JSON, with an actual object, in your case it should be look something like this: debug output:

Serialized storage: (storage:[geometry=myGeometry:[location=myLocation:[lat=41.156457, lng=-64.730457]], id=7c0ddc371afea935f81863ddfd9ebc1e813121b2, name=Establishment, place_id=ChIJ_bErEeHjt4kRlErHPKNZjAA, vicinity=7077 Main St, Chicago])

public class myLocation
{
    public Double lat {get;set;}
    public Double lng {get;set;}
    public myLocation(Double lat, Double lng)
    {
        this.lat = lat;
        this.lng = lng;
    }
}

public class myGeometry
{
    public myLocation location {get;set;}
    public myGeometry(myLocation location)
    {
        this.location = location;
    }
}

public class storage 
{
    public myGeometry geometry {get;set;}
    public String id {get;set;}
    public String name {get;set;}
    public String vicinity {get;set;}
    public String place_id {get;set;}

    public storage(myGeometry geometry, String id, 
                    String name, String vicinity, String place_id)
    {
        this.geometry = geometry;
        this.id = id;
        this.name = name;
        this.vicinity = vicinity;
        this.place_id = place_id;
    }
}

List<storage> storagelist = new List<storage>();
JSONparser parser = JSON.createparser(Results);
while (parser.nextToken() != null) 
{
    if (parser.getCurrentToken() == JSONToken.START_ARRAY)
    {
        while(parser.nextToken() != null)
        {
            if(parser.getCurrentToken() == JSONToken.START_OBJECT)
            {
                storage sto = (storage)parser.readValueAs(storage.class);
                storagelist.add(sto);
                System.debug('*****Serialized storage: ' + storagelist);
            }
        }
    }
}