apollo-core/src/main/java/com/ctrip/framework/apollo/core/utils/NetUtil.java/NetUtil/cleanUpConnection
class NetUtil:  private static void cleanUpConnection(HttpURLConnection conn) {
    InputStreamReader isr = null;
    InputStreamReader esr = null;
    try {
      isr = new InputStreamReader(conn.getInputStream(), StandardCharsets.UTF_8);
      CharStreams.toString(isr);
    } catch (IOException e) {
      InputStream errorStream = conn.getErrorStream();

      if (errorStream != null) {
        esr = new InputStreamReader(errorStream, StandardCharsets.UTF_8);
        try {
          CharStreams.toString(esr);
        } catch (IOException ioe) {
          //ignore
        }
      }
    } finally {
      if (isr != null) {
        try {
          isr.close();
        } catch (IOException ex) {
          // ignore
        }
      }

      if (esr != null) {
        try {
          esr.close();
        } catch (IOException ex) {
          // ignore
        }
      }
    }
  }