add 3.9 to coverage

Author: Cobalt

.github/workflows/ci.yml

@@ -117,7 +117,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [ '3.6', '3.7', '3.8' ]
+        python-version: [ '3.6', '3.7', '3.8', '3.9' ]
     services:
       postgres:
         image: fantix/postgres-ssl:13.1