util.promisify()でcallbackスタイルの関数をpromise化 ref: https://qiita.com/t-okushima/items/fbca67541003576997cc

file0.js

'use strct';

const fs = require('fs');
const util = require('util');

const readFileAsync = util.promisify(fs.readFile);

const filePath = './test.txt';

async function promisifyTest() {
    try {
        const text = await readFileAsync(filePath, {encoding : 'utf8'});
        console.log(text);
    } catch (error) {
        console.log(error);
    }
}

promisifyTest();

file0.txt

'use strct';

const fs = require('fs');
const util = require('util');

const readFileAsync = util.promisify(fs.readFile);

const filePath = './test.txt';

async function promisifyTest() {
    try {
        const text = await readFileAsync(filePath, {encoding : 'utf8'});
        console.log(text);
    } catch (error) {
        console.log(error);
    }
}

promisifyTest();