Add Nodejs 12 runtime support

[jaytula]

Is your feature request related to a problem? Please describe.

I am trying to import the npm library simple-oauth2 and use it with a netlify function
and also use netlify-lambda to test locally.

import simpleOauth from 'simple-oauth2'

export const handler = (event: APIGatewayEvent) => {
  return {
    statusCode: 200,
    body: 'Hello!!!'
  }
}

I believe that since the library depends on private class properties which is supported in
Nodejs 12 runtime, it will not work with netlify-lambda that appears to run with nodejs 8 runtime
according to the README.

Describe the solution you'd like

A way to choose the nodejs runtime by setting the environment variable locally perhaps like:

https://www.netlify.com/blog/2019/12/04/node.js-12-now-available-for-netlify-functions/

Additional context

An error like this happens when trying to require simple-oauth2 and using netlify-lambda serve:

oauth-netlify-practice/node_modules/simple-oauth2/lib/client.js:19
  #config = null;
  ^

SyntaxError: Invalid or unexpected token
    at Module._compile (internal/modules/cjs/loader.js:723:23)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
    at Module.load (internal/modules/cjs/loader.js:653:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
    at Function.Module._load (internal/modules/cjs/loader.js:585:3)
    at Module.require (internal/modules/cjs/loader.js:692:17)
    at require (internal/modules/cjs/helpers.js:25:18)
    at Object.<anonymous> (auth-netlify-practice/node_modules/simple-oauth2/index.js:3:16)
    at Module._compile (internal/modules/cjs/loader.js:778:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)

[erezrokah]

Hi @jaytula, do you mind sharing a repo reproducing this issue? It will make it easier to debug.

[jaytula]

@erezrokah Ok. Here is the repo:

https://github.com/jaytula/netlify-lambda-nodejs12-example

To reproduce the issue:

git clone https://github.com/jaytula/netlify-lambda-nodejs12-example
cd netlify-lambda-nodejs12-example
npm install
npm start

If you comment out the PROBLEM START to PROBLEM END in ./src/lambda/hello.ts, the http://localhost:9000/.netlify/functions/hello endpoint will work.

[erezrokah]

This might be a Webpack issue webpack/webpack#10216