const map = new Map();
pool.query(`SELECT * FROM trips WHERE destination = $1 AND begin_time >= $2 AND begin_time < $3 ORDER BY begin_time`, ['BROWNSVILLE ROCKAWAY AV', '2018-07-18 00:00-04:00', '2018-07-19 00:00-04:00'])
.then(async res1 => Promise.all(res1.map((r, i) => {
    if (res1[i + 1]) {
        return pool.query(`SELECT * FROM get_hwtable($1, $2)`, [r.trip_id, res1[i + 1].trip_id])
        .then(res => {
            const { rows: hwRows } = res;
            map.set([res1[i].trip_id, res1[i + 1].trip_id], hwRows);
        }).catch(e => console.log('20', e))
    }
})))
.catch(e => console.log('25', e))
.finally(function () {
    console.log(map);
});