Reduce tests on macOS and increase limit. Fixes #632

Author: m3nu

.github/workflows/main.yml

@@ -4,14 +4,20 @@ on: [push, pull_request]
 
 jobs:
   test:
-    timeout-minutes: 10
+    timeout-minutes: 15
     runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
 
       matrix:
         python-version: [3.6, 3.7, 3.8]
         os: [ubuntu-latest, macos-latest]
+        exclude:
+          # Only test Python 3.7 on macOS
+          - os: macos-latest
+            python-version: 3.6
+          - os: macos-latest
+            python-version: 3.8
 
     steps:
     - uses: actions/checkout@v2