HTTPClient returning nullreferenceobject from async GetRequest

I'm trying to access the php API on our server that basically outputs a json string as a result. The string is a list of json objects and I'm trying to deserialize them into a List of a class I have defined in the data model of my app. The problem is, when I try to just output the result in the console in my http testing project, I get a nullreferenceobject exception even though the address is completely correct and gives me a json object as expected.

Here is my async method in the myClient class:
public async Task<List> getUsers()
{
var client = new HttpClient();
// I just split up the entire address into baseAddress, the phpScript and the username so that I can change depending on what I need to Get from the server
var response = await client.GetAsync(baseAddress + phpScript + username);

            var userJson = response.Content.ReadAsStringAsync().Result;

            var rootObject = JsonConvert.DeserializeObject<userRoot>(userJson);

            return rootObject.users;
        }

Then in my test Program:
static void Main(string[] args)
{
var client = new myClient();

                var userList= client.getUserFriends(action, controller);

                foreach (User u in userList.Result)  // this is where it breaks telling me the object is null
                {
                    Console.WriteLine("Reading firstname: ");
                    Console.WriteLine(u.firstName);
                }
         }

Here is part of my model:
public class User
{
// class generated by copying the address into json2csharp.com
public string userID { get; set; }
public string firstName { get; set; }
public string lastName { get; set; }
public string userName { get; set; }
}

        public class userRoot // also generated by json2csharp.com
        {
             public List<User> users { get; set; }
             public bool sucess { get; set; }
        }

Like I mentioned, the address does respond with the correct json string, but there seems to be a problem somewhere in the conversion or the async method, I really can't tell what's going wrong...