This gist shows how to use ssh agent to run composer and npm install for packages from private repos in bitbucket through GitHub actions

github-actions.yml

name: SIMPLE ACTIONS

on:
  pull_request:
    branches: [ master, develop ]

jobs:
  simple-job:

    runs-on: ubuntu-latest

    steps:
    - uses: shivammathur/setup-php@15c43e89cdef867065b0213be354c2841860869e
      with:
        php-version: '8.1'

    - uses: webfactory/[email protected]
      with:
        ssh-private-key: ${{ secrets.PRIVATE_KEY }}

    - name: 'SSH: TRUST HOSTS'
      run: |
        ssh-keyscan bitbucket.org >> ~/.ssh/known_hosts
        ssh-keyscan github.com >> ~/.ssh/known_hosts

    - uses: actions/checkout@v3
    - name: Copy .env file
      run: php -r "file_exists('.env') || copy('.env.example', '.env');"

    - name: Install Compose Dependencies And Packages
      run: composer install -q --no-ansi --no-interaction --no-scripts --no-progress --prefer-dist

    - name: Install NPM Dependencies And Packages
      run: npm install --silent