title: OKHttp adding headers
body: <pre><code>final SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(mContext);
              final OkHttpClient okHttpClient = new OkHttpClient.Builder()
                      .addInterceptor(new Interceptor() {
                          @Override
                          public okhttp3.Response intercept(Interceptor.Chain chain) throws IOException {
                              Request.Builder ongoing = chain.request().newBuilder();
                              ongoing.addHeader("Cache-Control", "no-cache");
                              ongoing.addHeader("User-Agent", System.getProperty("http.agent"));
                              ongoing.addHeader("authorization", sharedPreferences.getString("api_key",""));
                              return chain.proceed(ongoing.build());
                          }
                      })
                      .build();
              new Picasso.Builder(mContext).downloader(new OkHttp3Downloader(okHttpClient)).build().with(mContext).load(event.getPictureUrl()).into(holder.eventimage);
  </code></pre>
  
  <p>I am using 
  <code>com.squareup.picasso:picasso:2.5.2</code> ,<code>com.jakewharton.picasso:picasso2-okhttp3-downloader:1.1.0</code>, <code>com.squareup.okhttp3:okhttp:3.4.1</code>
  and its not sending anything in the headers. How to solve this issue?</p>
  
  <p>Once I added this  Picasso.setSingletonInstance(picasso); And I used Picasso later on it worked.</p>