try updated workflow

Author: frank06

.github/workflows/test.yml

@@ -31,7 +31,7 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     steps:
-      - uses: dart-lang/setup-dart@v1.5
+      - uses: dart-lang/setup-dart@v1.6.2
       - uses: actions/checkout@v2
       - name: Install dependencies
         run: dart pub get