querySave.js

const queryDbAndSave = async(connection, sql, totalRecords, ts, s3key, bucket, output = 'local', dryRun = false) => {
    return new Promise((resolve, reject) => {
            if (output === 'local') {
            const outputStream = fs.createWriteStream('output.csv', { encoding: 'utf8' });
            s1.stream({ highWaterMark: BATCH_SIZE }) // stream() is just to wrap into pipeable object, and not to enable 'result' events, they are emitted anyway.
                .pipe(csvstringify({ header: true }))
                .pipe(outputStream)
                .on('finish', () => { resolve('saved data locally'); });
        });
}