SSIS package C# script task to make https call using httpClient

The separate console application works just fine and file gets downloaded through https call.

static void main()  {MainAsync().Wait();}

 static async Task MainAsync()    {}

We can't do the async call with SSIS package script task. I was trying to find a way to make https via httpClient but always returns result error(marked in bold). Any way to fix this one? I see my script task project target framework is .net 4.5

public void Main()
  {
            GetData();           
            Dts.TaskResult = (int)ScriptResults.Success;
  }

public static void GetData()
        {
   HttpClient client = new HttpClient();
            var byteArray = Encoding.ASCII.GetBytes(string.Format("{0}:{1}", "TestUser", "TestPass"));
            client.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Basic", Convert.ToBase64String(byteArray));
            HttpResponseMessage response = client.GetAsync("https://Report/OutboundA00&format=csv").Result;
            HttpContent content = response.Content;

            if (response.IsSuccessStatusCode)
            {
                var responseContent = response.Content;
                // by calling .Result you are synchronously reading the result
                string responseString = responseContent.ReadAsStringAsync().Result;
                //Console.WriteLine(responseString);
                System.IO.File.WriteAllText("c:\\csv_outbound.csv", responseString);
            }
  }

Appreciate either fix the above or any other sample where I can call https url to download the data(it takes 2 minutes hence webclient wont work)

Many thanks,