title: How do I convert this curl command to Objective-C?
body: <p>I want to get data from my backend. I should set a request header with Authorization and use the generate auth_token from my previous interaction to the backend. 
  here it is my curl</p>
  
  <pre><code>curl -H 'Authorization: Token token="replace-with-token"' http://domain.com/books
  </code></pre>
  
  <p>here it is my code</p>
  
  <pre><code>  NSURL *url = [NSURL URLWithString:@"http://domain.com/books"];
      config = [NSURLSessionConfiguration defaultSessionConfiguration];
      [config setHTTPAdditionalHeaders:@{@"token":@"4959a0bc00a15e335fb6"}];
      NSURLSession *session = [NSURLSession sessionWithConfiguration:config];
      [[session dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
          NSLog(@"%@", [NSJSONSerialization JSONObjectWithData:data options:0 error:nil]);
      }] resume];
  </code></pre>
  
  <p>I am not sure if I implemented the curl correctly. The data,which I received from backend, is null . Does any one know the reason?</p>