cron8.js

const admin = require('firebase-admin')
const serviceAccount = JSON.parse(process.env.FIREBASE_CRED_KEY)
// intialize app just once. Firebase will complain if we do it for each lambda execution
admin.initializeApp({
  credential: admin.credential.cert(serviceAccount),
  databaseURL: 'https://yourproject.firebaseio.com'
})
module.exports.lambda = async (event, context) => {
  /**
   * compose push notification message
   */
  const options = {
    priority: 'high',
    timeToLive: 60 * 60 * 24
  }
  const registrationToken = data.token
  const message = {
    notification: {
      title: 'Reminder',
      body: 'Don\'t forget your activities for today!'
    },
    data: { // metadata
      activities: data.activities.join(','),
    }
  }
  /**
   * send message
   */
  await admin.messaging().sendToDevice(registrationToken, message, options)
}