title: How to remove content-length header from http GET request in Flutter?
body: <p>I try to create a Flutter client app that communicates to REST API.
  When I create an HTTP GET request as below, it always includes <code>content-length:0</code> and the server returns <code>status code 400:Bad request</code>.
  If I send a request without this header by another tool, server returns <code>status code 200:OK</code>.</p>
  <pre><code>//import 'package:http/http.dart' as http;
  final client = http.Client();
  final response = await client.get(url);
  </code></pre>
  <p>or</p>
  <pre><code>//import 'package:dio/dio.dart';
  final options = BaseOptions();
  options.headers.remove(Headers.contentTypeHeader);
  options.headers.remove(Headers.contentLengthHeader);
  final dio = Dio(options);
  final response = await dio.get(url);
  </code></pre>
  <p>How can I remove this header?</p>