ci: test 4.0

Author: Agnes Lin

.github/workflows/continous-integration.yaml

@@ -2,10 +2,11 @@ name: Continous Integration
 
 on: # [push]
   push:
-    branches: [master]
+    branches:
+    - master
   pull_request:
-    # The branches below must be a subset of the branches above
-    branches: [master]
+    branches:
+    - master
 
 env:
   CI: true
@@ -16,8 +17,7 @@ jobs:
     strategy:
       matrix:
         node-version: [10, 12, 14]
-        # mongodb-3.2-precise
-        mongodb-version: [3.6]
+        mongodb-version: [4.0]
 
     steps:
     - name: Git checkout