try to use matrix for python version

.github/workflows/python-app.yml

@@ -19,20 +19,15 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
-    - name: Python version
-      id: get-python-version
-      run: |
-        echo "::set-output \"name=python::$(python --version)\""
-      shell: bash
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python-version }}
     - uses: actions/cache@v2
       with:
         path: |
           .venv
-        key: ${{ runner.os }}-${{ hashFiles('poetry.lock') }}-${{ steps.get-python-version.outputs.python }}
-    - name: Set up Python 3.8
-      uses: actions/setup-python@v2
-      with:
-        python-version: 3.8
+        key: ${{ runner.os }}-${{ hashFiles('poetry.lock') }}-${{ matrix.python-version }}
     - name: Install dependencies
       run: |
         pip install poetry
@@ -44,4 +39,3 @@ jobs:
     - name: Test with behave
       run: |
         poetry run behave --no-skipped --format progress2
-