build python 3.9

Author: hobu

.github/workflows/build.yml

@@ -19,7 +19,7 @@ jobs:
       fail-fast: true
       matrix:
         os: ['ubuntu-latest', 'macos-latest' ]
-        python-version: ['3.7','3.8']
+        python-version: ['3.7','3.8', '3.9']
 
     steps:
     - uses: actions/checkout@v2
@@ -61,7 +61,7 @@ jobs:
       fail-fast: true
       matrix:
         os: ['windows-latest']
-        python-version: ['3.7','3.8']
+        python-version: ['3.7','3.8', '3.9']
 
     steps:
     - uses: actions/checkout@v2