Add file header via swift format

.github/workflows/nightly.yml

@@ -6,6 +6,13 @@ on:
   workflow_dispatch:
 
 jobs:
+  macOS:
+    runs-on: macOS-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+    - name: SPM tests
+      run: swift test --sanitize=thread
   linux:
     runs-on: ubuntu-latest
     strategy: