title: Why onNext() and other methods don't work?
body: <p>I create <code>@GET</code> response with Retrofit2 but <code>onNext()</code>, <code>onError()</code> and <code>onComplete()</code> don't work.</p>
  
  <pre><code>retrofit = new Retrofit.Builder().baseUrl("https://gist.githubusercontent.com/MaxWBB/747f2eca800e05861bebc8f02ddb2721/raw/65673cae770b9b1fe8a668466868f1378e061f0d/").
              addConverterFactory(GsonConverterFactory.create()).addCallAdapterFactory(RxJava2CallAdapterFactory.create()).build();
      serverApi = retrofit.create(ServerApi.class);
      serverApi.getDatas().subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).subscribe(new DisposableObserver&lt;List&lt;Client&gt;&gt;() {
          @Override
          public void onNext(List&lt;Client&gt; clients) {
              tv1.setText(String.valueOf(clients.size()));
              Log.d("getData()","Works");
          }
  
          @Override
          public void onError(Throwable e){
              Log.d("OnError()","error:"+String.valueOf(e));
          }
  
          @Override
          public void onComplete() {
  
          }
      });
  </code></pre>