action.yml

# action.yml
name: 'Notify slack'
description: 'Notify slack from github action'

inputs:
  text:
    description: 'Message to send'
    required: true
    default: 'Ping'
  channel:
    description: 'Channel to notify, e.g. #my-channel'
    required: true
  token:
    description: 'Slack API token'
    required: true
    default: 'NO_TOKEN'

outputs:
  success:
    description: 'Whether request was successful'
    value: ${{ steps.notify.outputs.success }}

runs:
  using: "composite"
  steps: 
    - id: install
      shell: bash
      run: sudo apt-get install -y jq 
      
    - id: notify
      shell: bash
      env:
        TOKEN: ${{ inputs.token }}
        TEXT:  ${{ inputs.text }}
      run: |
        echo "Notifying ${{ inputs.channel }} via Slack..."
        
        echo "TEXT is:"
        echo $TEXT
        
        JSON='{
            "text": ":github: ${{ inputs.text }}", 
            "channel": "${{ inputs.channel }}", 
            "as_user": "True"
        }'
        RESULT=$( curl --location --request POST 'https://slack.com/api/chat.postMessage' \
        --header 'Content-Type: application/json' \
        --header "Authorization: Bearer $TOKEN" \
        --data-raw "${JSON}" )
        SUCCESS=$( echo $RESULT | jq -r '.ok' )
        
        echo "::set-output name=success::$(echo $SUCCESS)"
        if [ $SUCCESS != 'true' ]; then
          echo "Error when making request"
          echo $RESULT
          exit 1
        fi
        
        echo "Notified successfully"