Update build.yml

.github/workflows/build.yml

@@ -17,6 +17,14 @@ jobs:
         with:
           java-version: ${{ matrix.java }}
           distribution: 'adopt'
+      - uses: actions/cache@v2
+        with:
+          path: |
+            ~/.gradle/caches
+            ~/.gradle/wrapper
+          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle*', '**/gradle-wrapper.properties') }}
+          restore-keys: |
+            ${{ runner.os }}-gradle-
       - name: Build paperweight
         run: |
           git clone https://github.com/PaperMC/paperweight.git