try to use nightly toolchain

Author: colemanirby

.github/workflows/rust.yml

@@ -4,7 +4,6 @@ on:
   push:
     branches:
       - main
-      - cki/github-workflow
   pull_request:
     branches:
       - main
@@ -59,7 +58,7 @@ jobs:
       uses: taiki-e/install-action@nextest
 
     - name: Run Tests
-      run: cargo llvm-cov --cobertura --output-path cobertura.xml nextest
+      run: cargo +nightly llvm-cov --cobertura --output-path cobertura.xml nextest
 
     - name: Generate Code Coverage Summary
       uses: irongut/CodeCoverageSummary@v1.3.0