Use an unspported Node.js version in AWS Lambda (fusebit/anynode) (serverless-stack)

index.ts

#!/usr/bin/env node
import { App } from '@serverless-stack/resources';
import { request } from 'undici';

/** eg: `us-west-1`, `us-east-2` */
type AWSRegion = string;
/** eg: `18.4.0`, `16.14.0`, `14.17.0` */
type SemVersion = `${number}.${number}.${number}`;

/**
 * Fetches the FuseBit AnyNode lambda layer for all functions.
 * @param region AWS Region (eg: `us-west-1`, `us-east-2`)
 * @param nodeVersion Node Version (eg: `16.14.0`, `14.17.0`) (@default: `18.4.0`)
 * @returns AWS Lambda Layer ARN
 * @example
 * ```js
 * await fetchNodeLayer(app.region)
 * // => "arn:aws:lambda:us-west-1:072686360478:layer:node-18_4_0:1"
 * ```
 * @example
 * ```js
 * await fetchNodeLayer(app.region, '16.14.0')
 * // => "arn:aws:lambda:us-west-1:072686360478:layer:node-16_14_0:1"
 * ```
 */
async function fetchNodeLayer(region: AWSRegion, nodeVersion: SemVersion = '18.4.0') {
	const res = await request('https://cdn.fusebit.io/everynode/layers.json');
	// formatted like { 'region': { 'nodeVersion': 'layerArn' } }
	const body = (await res.body.json()) as Record<AWSRegion, Record<SemVersion, string>>;
	return body[region][nodeVersion];
}

export default async function main(app: App): Promise<void> {
	const nodeLayerArn = await fetchNodeLayer(app.region);
	// apply to all lambda functions
	app.setDefaultFunctionProps({
		layers: [nodeLayerArn],
	});

	//... business logic
}