few changes in workflow

Author: abhaykadam

.github/workflows/pythonpackage.yml

@@ -5,11 +5,12 @@ on: [push]
 jobs:
   build:
 
-    runs-on: [macos-latest, ubuntu-latest]
+    runs-on: ${{ matrix.os }}
     strategy:
       max-parallel: 4
       matrix:
         python-version: [2.7, 3.5, 3.6, 3.7, 3.8]
+        os: [ubuntu-latest, macos-latest]
 
     steps:
     - uses: actions/checkout@v1