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OOI Engineering

GH Action - Send a Slack message

We have a collection of GitHub Actions that can be used to implement common Workflows to improve the efficiency of your projects. Alongside these Actions are also pre-configured Workflows that implement the most common of these, for your convenience.

View the innovation-shared-actions repository (internal).

Slack notification workflow

Section titled “Slack notification workflow”

This is a GitHub Actions workflow that sends notifications to Slack channels. It supports posting a primary message and an optional threaded follow-up message. Repositories within the same GitHub organization can call this workflow to standardize Slack notifications across teams.

How it works

Section titled “How it works”

The Slack Notification workflow wraps the official slackapi/slack-github-action@v2 integration. It sends:

  1. A primary Slack message to a specified channel
  2. An optional threaded message using the timestamp of the first message

It calls Slack’s chat.postMessage API method under the hood. Read more at the Slack action notification.

Requirements

Section titled “Requirements”

Repo must be in the same organization

Section titled “Repo must be in the same organization”

This workflow consumes an organization-level secret. GitHub only allows access to shared workflow secrets if the calling repository is in the same GitHub org.

Add the Slack notification bot to your Slack channel

Section titled “Add the Slack notification bot to your Slack channel”

Slack will block messages unless the bot is a member of the channel.

To add the bot:

  1. Open the Slack channel
  2. Add “Notification Bot” to the channel
  3. Ensure the bot appears in the channel’s integrations list

If you need to make changes to the Slack bot or need to access the key directly, reach out to Tech Ops so you can be added as a collaborator.

Required secret: SLACK_OAUTH_TOKEN

Section titled “Required secret: SLACK_OAUTH_TOKEN”

The workflow expects a secret named: SLACK_OAUTH_TOKEN (this is already installed)

This is configured as an organization secret, accessible to any repo using the workflow.

Inputs

Section titled “Inputs”
NameRequiredTypeDescription
channel_idYesstringSlack channel ID (ex: C09Q34G9HMX).
messageYesstringMain message posted to the channel.
thread_messageNostringOptional threaded message.

Using this workflow in your repository

Section titled “Using this workflow in your repository”

Create a new workflow file, e.g. .github/workflows/notify.yml:

name: "Notify Slack"


on:
  workflow_dispatch: ## replace this with how you want to trigger the notification


jobs:
  notify-slack:
    uses: newjersey/innovation-shared-actions/.github/workflows/slack.yml@main
    with:
      channel_id: C09Q34G9HMX
      message: "Something cool happened!"
      thread_message: "And everything is great!" # optional
    secrets: inherit

Slack Message Action

Section titled “Slack Message Action”

If you find yourself limited by it, instead of using the above workflow you can use the underlying Action directly. This gives you a bit more composability for building more complex workflows.

How it works

Section titled “How it works”

Just like the workflow above, the action handles:

  1. Sending a primary message to a Slack channel
  2. Optionally sending a threaded reply using the timestamp from the first message
  3. Returning the message timestamp for potential use in subsequent steps

Requirements

Section titled “Requirements”

Slack OAuth Token

Section titled “Slack OAuth Token”

You’ll need access to a Slack OAuth token with the necessary permissions to post messages. Likely, the organization secret SLACK_OAUTH_TOKEN will be sufficient, if not, you’ll need to create another Slack Bot or request additional permissions for the existing one.

Bot must be added to the channel

Section titled “Bot must be added to the channel”

Same requirement as the workflow - the Slack bot must be a member of the target channel.

Inputs

Section titled “Inputs”
NameRequiredTypeDescription
channel_idYesstringSlack channel ID (ex: C09Q34G9HMX).
messageYesstringMain message posted to the channel.
thread_messageNostringOptional threaded message.
tokenYesstringSlack OAuth token.

Outputs

Section titled “Outputs”
NameDescription
message_tsTimestamp of the main message sent.

Using this action in your repository

Section titled “Using this action in your repository”
name: "Custom Slack Workflow"


on:
  workflow_dispatch:


jobs:
  custom-notification:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v6


      - name: Send Slack message
        id: slack
        uses: newjersey/innovation-shared-actions/.github/actions/slack-message@main
        with:
          channel_id: C09Q34G9HMX
          message: "Build completed successfully!"
          thread_message: "All tests passed ✅"
          token: ${{ secrets.SLACK_OAUTH_TOKEN }}


      - name: Use message timestamp
        run: |
          echo "Message sent at: ${{ steps.slack.outputs.message_ts }}"

References for the Slack notification workflow

Section titled “References for the Slack notification workflow”