Add Python 3.9 to test matrix (#222)

* Add Python 3.9 to test matrix

* Update to setup-python@v2

Co-authored-by: jianghang <jianghang@didiglobal.com>

Author: florimondmanca

.github/workflows/test-suite.yml

@@ -14,11 +14,11 @@ jobs:
 
     strategy:
       matrix:
-        python-version: ["3.6", "3.7", "3.8"]
+        python-version: ["3.6", "3.7", "3.8", "3.9"]
 
     steps:
       - uses: "actions/checkout@v2"
-      - uses: "actions/setup-python@v1"
+      - uses: "actions/setup-python@v2"
         with:
           python-version: "${{ matrix.python-version }}"
       - name: "Install dependencies"