report.js

const http = require('https');

const postToSlack = (data) => {
  const host = 'hooks.slack.com';
  const hookUrl = 'slack hook path';
  return new Promise((resolve, reject) => {
    const options = {
      host,
      path: hookUrl,
      method: 'POST',
      headers: {
        "Content-Type": "application/json",
        'Content-Length': Buffer.byteLength(data)
      }
    };
    const req = http.request(options, (res) => {
      res.on('end', () => {
        res.statusCode === 200
          ? resolve()
          : reject()
      });
    });
    req.write(data);
    req.end();
  });
}

exports.handler = async (event, context, callback) => {
  // get the message passed to the subscription from the SNS topic
  const message = JSON.parse(event.Records[0].Sns.Message);
  const host = 'hooks.slack.com';
  const hookUrl = '/services/T5ULH901M/BHJ5Y57L2/vZaz2zB7TemNm7t8ofPrc9ns';
  const slackMsg = JSON.stringify({
    text: `Update on ${message.Trigger.Dimensions[0].value}`,
    attachments: [{
      text: message.NewStateReason,
      fields: [{
        title: 'Lambda Function',
        value: message.Trigger.Dimensions[0].value,
        short: true,
      }, {
        title: 'Time',
        value: message.StateChangeTime,
        short: true,
      }, {
        title: 'Alarm',
        value: message.AlarmName,
        short: true,
      }, {
        title: 'Region',
        value: message.Region,
        short: true,
      }],
    }]
  });
  
  try {
    await postToSlack(slackMsg);
    callback();
  } catch(error) {
    callback(error)
  }
};