How to: await / async in a node.js lambda function?

Question

I am trying to create an async lambda function that makes a http Get call put it's not working correctly and I believe it has to do with it being async. If I remove await/async , and make it synchronous, my function works correctly. I'm not sure what I am doing wrong. Thank you for your help!

exports.handler = async function (event, context) {

    await setBattery();

    // TODO implement
    const response = {
        statusCode: 200,
        body: JSON.stringify('Hello from Lambda!'),
    };
    return response;
};

async function setBattery() {
    'use strict';

    const https = require('https');

    const options = {
        hostname: 'testsite.com',
        port: 443,
        path: '/proxy/api/setting?EM_OperatingMode=1',
        method: 'GET',
        headers: {
            'Content-Type': 'application/json',
        }
    };

    const req = https.request(options, res => {
        console.log(`statusCode: ${res.statusCode}`);

        res.on('data', d => {
            process.stdout.write(d);
        });
    });

    req.on('error', error => {
        console.error(error);
    });

    req.end();

}

Answer 1

According with MDN Web Docs:

The async function declaration defines an asynchronous function, which returns an AsyncFunction object. An asynchronous function is a function which operates asynchronously via the event loop, using an implicit Promise to return its result . But the syntax and structure of your code using async functions is much more like using standard synchronous functions.

So, You need to return a Promise object in order to be handled by your async function (You could also use another promise to handle it), I converted setBattery to a normal function and the return of this function is now a promise that will be handled by your handler ( exports.handler ). I haven't tested the code but it should work.

exports.handler = async function (event, context) {

    await setBattery();

    // TODO implement
    const response = {
        statusCode: 200,
        body: JSON.stringify('Hello from Lambda!'),
    };
    return response;
};

function setBattery() {
    'use strict';

    const https = require('https');

    const options = {
        hostname: 'testsite.com',
        port: 443,
        path: '/proxy/api/setting?EM_OperatingMode=1',
        method: 'GET',
        headers: {
            'Content-Type': 'application/json',
        }
    };

    // Return it as a Promise
    return new Promise((resolve, reject) => {

        const req = https.request(options, res => {
            console.log(`statusCode: ${res.statusCode}`);

            res.on('data', d => {
                process.stdout.write(d);

                // If successful
                resolve(d);
            });
        });

        req.on('error', error => {
            console.error(error);

            // If failed
            reject(error);
        });

        req.end();

    });

}