HMRC Hello World

namespace consoleapp1 
{ 
  class Program 
  { 
    private static readonly 
    System.Net.Http.HttpClient client = new System.Net.Http.HttpClient(); 

    //-------------------------------------------------------------------------------------- 
    static async 
    System.Threading.Tasks.Task 
    Main(string[] args) 
    { 
      var response = await Method_HelloWorld(); 

      System.Console.WriteLine(response); 
    } 
    //-------------------------------------------------------------------------------------- 
    private static async 
    System.Threading.Tasks.Task<string> 
    Method_HelloWorld() 
    { 
      client.DefaultRequestHeaders.Accept.Clear(); 

      client.DefaultRequestHeaders.Accept.Add( 
          new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/vnd.hmrc.1.0+json")); 

      System.Net.Http.HttpResponseMessage response = 
      await client.GetAsync("https://test-api.service.hmrc.gov.uk/hello/world"); 

      string response_string = 
      await response.Content.ReadAsStringAsync(); 

      if (response is not null) 
      { 
        return response_string; 
      } 
      else 
      { 
        return ""; 
      } 
    } 
    //-------------------------------------------------------------------------------------- 
  } 
}