manually select xcode 11

.github/workflows/ci.yml

@@ -3,17 +3,15 @@ on: [push, pull_request]
 jobs:
   test:
     runs-on: macos-latest
-    name: Test ${{ matrix.xcode_version }}
-    strategy:
-      matrix:
-        xcode_version: ['10.3', '11_beta']
+    name: Test Swift 5
     steps:
     - uses: actions/checkout@master
+    - name: Xcode version
+      run: sudo xcode-select -s /Applications/Xcode_11_beta.app
     - name: Info
       run: |
         swift --version
         swift package --version
-        xcode-select -p
     - name: Resolve
       run: swift package resolve
     - name: Build