Swatinem/rust-cacheを使うようにした

Author: hotate29

.github/workflows/ci.yml

@@ -39,15 +39,10 @@ jobs:
     steps:
       - uses: actions/checkout@v2
 
-      - name: Cache cargo registry
-        uses: actions/cache@v2
+      - name: Cache dependencies
+        uses: Swatinem/rust-cache@v1.3.0
         with:
-          path: |
-            ~/.cargo/git
-            ~/.cargo/registry/cache
-            ~/.cargo/registry/index
-            ./atcoder-problems-backend/target
-          key: ${{ runner.os }}-cargo-${{ hashFiles('atcoder-problems-backend/Cargo.lock') }}
+          working-directory: ./atcoder-problems-backend
 
       - name: Setup Postgresql
         run: psql ${SQL_URL} < ../config/database-definition.sql