act/.github/actions/composite/action.yml

name: 'Test Composite Action'
description: 'Test Composite Action'
inputs:
  input:
    description: 'String to echo'
    required: true
    default: 'Hello World'
outputs:
  output:
    description: 'Output string'
    value: ${{ steps.set-output.outputs.string }}
runs:
  using: 'composite'
  steps:
    - run: echo Hello ${{ inputs.input }}.
      shell: bash
    - id: set-output
      run: echo "::set-output name=string::output string"
      shell: bash
    - run: |
        ${{ github.action_path }}/script.sh
      shell: bash