Try caching Maven dir.

.gitlab-ci.yml

@@ -1,3 +1,10 @@
+variables:
+  MAVEN_OPTS: "-Dmaven.repo.local=$CI_PROJECT_DIR/.m2/repository -Dorg.slf4j.simpleLogger.log.org.apache.maven.cli.transfer.Slf4jMavenTransferListener=WARN -Dorg.slf4j.simpleLogger.showDateTime=true"
+
+cache:
+  paths:
+    - .m2/repository
+
 image: maven:latest
 
 stages: