Lint on py3{6,7,8,9,10}

Co-authored-by: WangWeimin <wang0.618@qq.com>

.github/workflows/lint.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.6", "3.7", "3.8", "3.10"]
+        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10"]
 
     steps:
       - uses: actions/checkout@v2