Run tests across different OS's

Author: mislav

.github/workflows/push.yml

@@ -3,11 +3,15 @@ on: [push, pull_request]
 name: CI
 jobs:
   test:
-    runs-on: ubuntu-latest
     strategy:
       matrix:
-        go: [ '1.15' ]
-    name: Go ${{ matrix.go }} test
+        go: [ '1.13', '1.15' ]
+        os: [ ubuntu-latest, macos-latest, windows-latest ]
+      fail-fast: false
+    
+    runs-on: ${{ matrix.os }}
+    name: Test suite
+
     steps:
       - uses: actions/checkout@v2
       - name: Setup go