remove unnecessary toolchain and add cache to lint job

Author: yuk1ty

.github/workflows/rust.yml

@@ -24,6 +24,17 @@ jobs:
           profile: minimal
           components: rustfmt, clippy
 
+      - uses: actions/cache@v2
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-${{ github.job }}-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-${{ github.job }}-
+            ${{ runner.os }}-cargo-
+
       - name: cargo fmt
         uses: actions-rs/cargo@v1
         with:
@@ -48,7 +59,6 @@ jobs:
         uses: actions-rs/toolchain@v1
         with:
           profile: minimal
-          components: rustfmt, clippy
 
       - uses: actions/cache@v2
         with: