SOURCE

function sleep(second, param) {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            resolve(param);
        }, second);
    })
}

async function test() {
    let result1 = await sleep(2000, 'req01');
    // let result2 = await sleep(1000, 'req02' + result1);
    // let result3 = await sleep(500, 'req03' + result2);
    console.log(`
        ${result1}
    `);
}

test();