Try it, it works for me:
'use strict'
let fs = require("fs");
let path = require("path");
exports.handler = (event, context, callback) => {
console.log(path.resolve("./readme.txt"));
fs.readFile(__dirname +'/readme.txt', function (err, data) {
if (err) throw err;
});
};
to debug why your code is not working, add the link below to your handler
console.log(path.resolve("./readme.txt"));
AWS Lambda node - readme.txt , relative, absolute.