Merge pull request #25 from utgwkk/ci-python-version

ci: change Python version set

Author: utgwkk

.github/workflows/test.yml

@@ -12,7 +12,12 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, windows-latest]
-        python-version: [2.7, 3.5, 3.6, 3.7, 3.8]
+        python-version:
+          - '2.7'
+          - '3.6'
+          - '3.7'
+          - '3.8'
+          - '3.9'
         pytest-version: [4.6.11, 5.4.3]
 
         exclude: