readStdIn is an awaitable naive function which reads all input from stdin as a single, new-line preserved string,

readStdIn.js

import readline from 'readline';

async function readStdIn() {
  return new Promise((resolve, reject) => {
    const rl = readline.createInterface({ input: process.stdin, output: process.stdout });

    let input = '';

    rl.on('line', (line) => {
      input += line;
      input += '\n';
    });

    rl.on('close', () => {
      resolve(input);
    });

    // in case no input is provided, we don't want to block forever
    setTimeout(() => {
      if (input === '') {
        rl.close();
      }
    }, 50);
  });
}