Use nightly rustfmt.

Author: Dirbaio

.github/workflows/rustfmt.yml

@@ -13,7 +13,7 @@ jobs:
       - uses: actions-rs/toolchain@v1
         with:
           profile: minimal
-          toolchain: stable
+          toolchain: nightly
           override: true
           components: rustfmt
       - uses: actions-rs/cargo@v1