docs: public static PrivateKey readPrivateKey(String pemResName) throws Exception {
          InputStream contentIS = TokenUtils.class.getResourceAsStream(pemResName);
          byte[] tmp = new byte[4096];
          int length = contentIS.read(tmp);
          PrivateKey privateKey = decodePrivateKey(new String(tmp, 0, length));
          return privateKey;
      }