try this

based on
trautonen/coveralls-maven-plugin#136 (comment)

.github/workflows/tests.yaml

@@ -20,4 +20,13 @@ jobs:
           mysql user: 'root'
           mysql root password: 'root'
       - name: Run tests with Maven
-        run: mvn test jacoco:report coveralls:report -B -q --define repoToken=${{ secrets.COVERALLS_REPO_TOKEN }}
+        run:  |
+          export CI_BRANCH=${BRANCH_NAME_OR_REF#refs/heads/}
+          export CI_PULL_REQUEST=$(jq --raw-output .pull_request.number "$GITHUB_EVENT_PATH")
+          mvn test jacoco:report coveralls:report -B -q -DrepoToken=$COVERALLS_SECRET
+        env:
+          CI_NAME: github
+          BRANCH_NAME_OR_REF: ${{ github.head_ref || github.ref }}
+          CI_BUILD_NUMBER: ${{ github.run_id }}
+          CI_BUILD_URL: https://github.com/${{ github.repository }}/commit/${{ github.event.after }}/checks
+          COVERALLS_SECRET: ${{ secrets.GITHUB_TOKEN }}