Add cargo caching

Author: casibbald

.github/workflows/ci.yml

@@ -29,6 +29,31 @@ jobs:
           toolchain: nightly
           override: true
 
+      # Cache Cargo dependencies
+      - name: Cache Cargo registry
+        uses: actions/cache@v3
+        with:
+          path: ~/.cargo/registry
+          key: ${{ runner.os }}-cargo-registry-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-registry-
+
+      - name: Cache Cargo index
+        uses: actions/cache@v3
+        with:
+          path: ~/.cargo/git
+          key: ${{ runner.os }}-cargo-index-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-index-
+
+      - name: Cache target directory
+        uses: actions/cache@v3
+        with:
+          path: target
+          key: ${{ runner.os }}-cargo-target-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-target-
+
       # Install Rust dependencies
       - name: Install dependencies
         run: cargo fetch