code: function performParallel(pool, queries, callback) {
    let count   = 0,
        results = new Array(queries.length);
  
    queries.forEach((query, index) => {
      pool.query(query, (error, result) => {
        if (error) {
          return callback(error, results);
        }
  
        results[index] = result;
  
        if (++count === queries.length) {
          return callback(null, results);
        }
      });
    });
  }
docs: Using the specified connection pool, performs a series of specified queries
  in parallel, executing a specified callback function once all queries have
  successfully completed.
  @param  {BoundPool}      pool
  @param  {Array.<Object>} queries
  @param  {Function}       callback
  @private