Actions: Add Python 3.9

.github/workflows/mac.yml

@@ -35,6 +35,23 @@ jobs:
           pytest -v test
 
 
+      - name: Set up Python 3.9
+        uses: actions/setup-python@v1
+        with:
+          python-version: "3.9"
+
+      - name: Build wheel
+        run: |
+          pip install setuptools wheel
+          python setup.py bdist_wheel
+
+      - name: Run test
+        run: |
+          pip install pytest
+          pip install -v msgpack --only-binary :all: -f dist/ --no-index
+          pytest -v test
+
+
       - name: Set up Python 3.7
         uses: actions/setup-python@v1
         with: