Example Let's Encrypt configuration for KeystoneJS

server.js

const keystone = require('keystone')

keystone.init({
	name: 'myApp',
	brand: 'My App',

	port: process.env.PORT,
	'ssl port': process.env.SSLPORT,
	ssl: 'force',

	letsencrypt: (process.env.NODE_ENV === 'production') && {
		email: 'admin@myapp.com',
		domains: ['www.myapp.com', 'myapp.com'],
		register: true,
		tos: true,
	},

	...
})

IMPORTANT: per this thread, you must add "production: true" in the letsencrypt object.