code: function addXSetMember (key, timestamp, field, value, res, next) {
    let redisConnection = res.locals.connection;
    myutil.decodeHTMLEntities(field, function (decodedField) {
      myutil.decodeHTMLEntities(value, function (decodedValue) {
        redisConnection.xadd(key, timestamp, decodedField, decodedValue, function (err) {
          if (err) {
            console.error('addXSetMember', err);
            return next(err);
          }
          return res.send('ok');
        });
      });
    });
  }
docs: Stream related functions (XSet) - only add and delete allowed, no edit