Cache ~/.m2 dir for GitHub builds.
diff --git a/.github/workflows/maven.yml b/.github/workflows/maven.yml
index 1c8f0da..0256b2e 100644
--- a/.github/workflows/maven.yml
+++ b/.github/workflows/maven.yml
@@ -32,6 +32,12 @@
         
     steps:
     - uses: actions/checkout@v2.3.2
+    - uses: actions/cache@v2
+      with:
+        path: ~/.m2/repository
+        key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
+        restore-keys: |
+          ${{ runner.os }}-maven-
     - name: Set up JDK ${{ matrix.java }}
       uses: actions/setup-java@v1.4.0
       with: