adding cache key

Author: PicoCreator

.github/workflows/gradle-build.yml

@@ -18,6 +18,7 @@ jobs:
     - name: Cache Gradle packages
       uses: actions/cache@v2
       with:
+        key: ${{ runner.os }}-build-${{ env.cache-name }}-${{ hashFiles('**/build.gradle') }}
         path: |
           ~/.gradle/caches
           ~/.gradle/wrapper

.github/workflows/mysql-5-7.yml

@@ -31,6 +31,7 @@ jobs:
     - name: Cache Gradle packages
       uses: actions/cache@v2
       with:
+        key: ${{ runner.os }}-build-${{ env.cache-name }}-${{ hashFiles('**/build.gradle') }}
         path: |
           ~/.gradle/caches
           ~/.gradle/wrapper

.github/workflows/mysql-8.yml

@@ -31,6 +31,7 @@ jobs:
     - name: Cache Gradle packages
       uses: actions/cache@v2
       with:
+        key: ${{ runner.os }}-build-${{ env.cache-name }}-${{ hashFiles('**/build.gradle') }}
         path: |
           ~/.gradle/caches
           ~/.gradle/wrapper