message: use nightly in CI
diff: @@ -15,8 +15,9 @@ jobs:
  - name: Install Rust
  uses: actions-rs/toolchain@v1
  with:
  - toolchain: stable
  + toolchain: nightly-2021-02-15
  components: rustfmt
  + default: true
  - name: Is the code formatted?
  uses: actions-rs/cargo@v1
  