check for linux, win, mac

Author: digitronik

.github/workflows/main.yml

@@ -4,9 +4,10 @@ on: [push, pull_request]
 
 jobs:
   build:
-    runs-on: ubuntu-16.04
+    runs-on: ${{ matrix.operating-system }}
     strategy:
       matrix:
+        operating-system: [ubuntu-latest, windows-latest, macos-latest]
         python-version: [ '3.6', '3.7' ]
     name: Python ${{ matrix.python-version }}
     steps: