Update codecov.yml

.github/workflows/codecov.yml

@@ -1,20 +1,25 @@
 name: Codecov Report
-on: [push]
+
+on:
+  push:
+    branches: [ main ]
+
 jobs:
   run:
-    runs-on: ${{ matrix.os }}
+    runs-on: ubuntu-latest
     strategy:
+      fail-fast: false
       matrix:
-        os: [ubuntu-latest, macos-latest, windows-latest]
+        python-version: [3.5, 3.6, 3.7, 3.8, 3.9]
+
     env:
-      OS: ${{ matrix.os }}
-      PYTHON: '3.7'
+      PYTHON: ${{ matrix.python-version }}
     steps:
-    - uses: actions/checkout@master
+    - uses: actions/checkout@v2
     - name: Setup Python
-      uses: actions/setup-python@master
+      uses: actions/setup-python@v2
       with:
-        python-version: 3.7
+        python-version: ${{ matrix.python-version }}
     - name: Generate coverage report
       run: |
         pip install pytest
@@ -25,7 +30,7 @@ jobs:
       with:
         token: ${{ secrets.CODECOV_TOKEN }}
         directory: ./coverage/reports/
-        env_vars: OS,PYTHON
+        env_vars: PYTHON
         fail_ci_if_error: true
         files: ./coverage1.xml,./coverage2.xml
         flags: unittests