Object reference not set to an instance of an object. Source=Trail05 StackTrace

I am trying to get JSON data by http url and write it on console application but getting bellow error:

System.NullReferenceException HResult=0x80004003 Message=Object reference not set to an instance of an object. Source=Trail05 StackTrace: at ReadCountryData.Program.Main(String[] args) in D:\CSOM_Dev\ENRICH TRAIL\Trail05\Trail05\Program.cs:line 45

Below is the Request URL:

"https://services.odata.org/V3/Northwind/Northwind.svc/Customers?$format=json"

Code:

using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Web;
namespace ReadCountryData
{
    class Program
    {
    public class positionsobj
        {
            public positionlist positions { get; set; }
        }
        public class positionlist
        {
            public List<position> position { get; set; }
        }
           public class position
        {
            public string CustomerID { get; set; }
            public string CompanyName { get; set; }
        }

    static void Main(string[] args)
        {
            HttpClient http = new HttpClient();
            string url = "https://services.odata.org/V3/Northwind/Northwind.svc/Customers?$format=json";
            HttpResponseMessage response = http.GetAsync(new Uri(url)).Result;
            var responseBody = response.Content.ReadAsStringAsync().Result;
            Console.WriteLine(responseBody);
            positionsobj position = JsonConvert.DeserializeObject<positionsobj>(responseBody);
            foreach (position item in position.positions.position)
            {
                Console.WriteLine("{0}", item.CustomerID);
            }
            Console.ReadLine();
        }
    }
}