Correct worflow

.github/workflows/app.yml

@@ -9,6 +9,9 @@ on:
 jobs:
   lint-and-test:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: [3.8, 3.9, 3.10]
 
     steps:
     - name: Checkout code
@@ -17,7 +20,7 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v2
       with:
-        python-version: 3.8, 3.9, 3.10
+        python-version: ${{ matrix.python-version }}
 
     - name: Install dependencies
       run: |