OrientDB.ConnectionError [10]
const boostrap = pool => {
  app.use((req, res, next) => {
    pool
      .acquire()
      .then(session => {
        res.locals.db = session;
        res.on('end', () => {
          console.log('end : closing db session...');
          if (session) {
              session.close();
              session = null;
          };
        });
        res.on('close', () => {
          console.log('close : closing db session...');
          if (session) {
              session.close();
              session = null;
          };
        });
        res.on('finish', () => {
          console.log('finish : closing db session...');
          if (session) {
              session.close();
              session = null;
          };
        });
        next();
      })
      .catch(err => {
        console.log('err : closing db session...');
        if (session) {
            session.close();
            session = null;
        };
        res.status(500).send(err);
      });
  });
