index.js

const core = require('@actions/core');

const slack_webhook = core.getInput('slack_webhook', {
  required: true
});
const slack = require('slack-notify')(slack_webhook);

slack.onError = function (err) {
  core.error(`Error ${err}, action may still succeed though`);
};

// most @actions toolkit packages have async methods
async function run() {
  try {
    let attachment = {};
    attachment.fallback = core.getInput('fallback', {
      required: false
    });
    attachment.color = core.getInput('color', {
      required: false
    });
    attachment.pretext = core.getInput('pretext', {
      required: false
    });
    attachment.author_name = core.getInput('author_name', {
      required: false
    });
    attachment.author_link = core.getInput('author_link', {
      required: false
    });
    attachment.author_icon = core.getInput('author_icon', {
      required: false
    });
    attachment.title = core.getInput('title', {
      required: false
    });
    attachment.title_link = core.getInput('title_link', {
      required: false
    });
    attachment.text = core.getInput('text', {
      required: false
    });
    attachment.image_url = core.getInput('image_url', {
      required: false
    });
    attachment.thumb_url = core.getInput('thumb_url', {
      required: false
    });
    attachment.footer = core.getInput('footer', {
      required: false
    });
    attachment.footer_icon = core.getInput('footer_icon', {
      required: false
    });

    const channel = core.getInput('channel', {
      required: true
    });
    const icon_url = core.getInput('icon_url', {
      required: true
    });
    const username = core.getInput('username', {
      required: true
    });

    const default_attachment = {
      "title": `${process.env.GITHUB_REPOSITORY}`,
      "title_link": `https://github.com/${process.env.GITHUB_REPOSITORY}`,
      "color": attachment.color,
      "text": `${process.env.GITHUB_REF}`,
      "author_name": `${process.env.GITHUB_ACTOR}`,
      "author_link": `https://github.com/${process.env.GITHUB_ACTOR}`,
      "author_icon": `https://github.com/${process.env.GITHUB_ACTOR}.png`,
      "footer": `action -> ${process.env.GITHUB_EVENT_NAME}`,
      "thumb_url":"https://avatars0.githubusercontent.com/u/44036562?s=200&v=4"
    }

    var final_attachment = {};
    if (attachment.length == 0) {
      final_attachment = default_attachment;
    } else {
      final_attachment = attachment;
    }

    slack.send({
      channel: channel,
      icon_url: icon_url,
      username: username,
      attachments: [ final_attachment ]
    });
  } catch (error) {
    core.setFailed(error.message);
  }
}

run()