Update ci.yaml (#241)

diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index b6a3092..0f10aa7 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -21,7 +21,7 @@
         sdk: [dev]
     steps:
     - uses: actions/checkout@v2
-    - uses: dart-lang/setup-dart@v0.3
+    - uses: dart-lang/setup-dart@v1
       with:
         sdk: ${{ matrix.sdk }}
     - id: install
@@ -66,10 +66,10 @@
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        sdk: [dev]
+        sdk: [2.12.0, dev]
     steps:
     - uses: actions/checkout@v2
-    - uses: dart-lang/setup-dart@v0.3
+    - uses: dart-lang/setup-dart@v1
       with:
         sdk: ${{ matrix.sdk }}
     - uses: browser-actions/setup-geckodriver@v0.0.0