Example workflow that self terminates if another instance of same workflow is running

test_terminate_duplicate.yml

name: test_terminate_duplicate
on:
  workflow_dispatch
jobs:
  check_duplicate:
    runs-on: ubuntu-latest
    env:
      GH_TOKEN: ${{ github.token }}    
    steps:
      - name: show_vars
        run: |
          echo GITHUB_ACTION = "${GITHUB_ACTION}"
          echo GITHUB_ACTION_PATH = "${GITHUB_ACTION_PATH}"
          echo GITHUB_REPOSITORY = "${GITHUB_REPOSITORY}"
          echo GITHUB_REPOSITORY_ID = "${GITHUB_REPOSITORY_ID}"
          echo GITHUB_ACTION_REPOSITORY = "${GITHUB_ACTION_REPOSITORY}"
          echo GITHUB_RUN_ID = "${GITHUB_RUN_ID}"
          echo GITHUB_RUN_NUMBER = "${GITHUB_RUN_NUMBER}"
          echo GITHUB_JOB = "${GITHUB_JOB}"
          echo GITHUB_WORKFLOW = "${GITHUB_WORKFLOW}"
      - name: check_same_workflow
        run: |
          NUM_EXISTING=$(gh run -R "${GITHUB_REPOSITORY}" list -w "${GITHUB_WORKFLOW}" --json name,status,number | \
          jq --argjson jnum ${GITHUB_RUN_NUMBER} '[ .[] | select((.number!=$jnum) and (.status | IN ("pending","queued","in_progress"))) ] | length')
          echo NUM_EXISTING = ${NUM_EXISTING}
          if (( $NUM_EXISTING > 0 )); then
            echo "Duplicate run. Aborting."
            exit 1
          fi
      - name: sleep a while
        run: |
          echo "Sleeping for 30 seconds..."
          sleep 30