Run check on Ubuntu & iosX64Test on macOS

.github/workflows/ci.yaml

@@ -4,7 +4,11 @@ on: [ push, pull_request ]
 
 jobs:
   check:
-    runs-on: macos-latest
+    runs-on: ${{ matrix.os }}
+
+    strategy:
+      matrix:
+        os: [ ubuntu-latest, macos-latest ]
 
     steps:
       - uses: actions/checkout@v2
@@ -28,6 +32,10 @@ jobs:
           java-version: 1.8
 
       - run: ./gradlew check
+        if: matrix.os == 'ubuntu-latest'
+
+      - run: ./gradlew iosX64Test
+        if: matrix.os == 'macos-latest'
 
   publish:
     needs: check