fix setup

pkgs/test_reflective_loader/.github/workflows/build.yaml

diff --git a/pkgs/test_reflective_loader/.github/workflows/build.yaml b/pkgs/test_reflective_loader/.github/workflows/build.yaml
index 050ea78..18269d4 100644
--- a/pkgs/test_reflective_loader/.github/workflows/build.yaml
+++ b/pkgs/test_reflective_loader/.github/workflows/build.yaml
@@ -15,6 +15,9 @@
 
     steps:
       - uses: actions/checkout@v2
+      - uses: dart-lang/setup-dart@v1
+        with:
+          sdk: dev
 
       - name: pub get
         run: pub get