update

.github/workflows/coverage.yml

@@ -7,6 +7,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v1
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: nightly
+          override: true
       - uses: actions-rs/cargo@v1
         with:
           command: clean