ci(drone): 添加 Go 模块和构建缓存

- 在 restore cache 和 rebuild cache 步骤中添加了 go-mod-cache 和 go

.drone.yml

@@ -33,6 +33,14 @@ steps:
       - ls -lR /opt/drone/cache/go-mod || echo "/opt/drone/cache/go-mod not found"
       - echo "==== After build, /opt/drone/cache/go-build ===="
       - ls -lR /opt/drone/cache/go-build || echo "/opt/drone/cache/go-build not found"
+      - echo "==== Whoami and permissions ===="
+      - whoami
+      - id
+      - ls -ld /opt/drone/cache/go-mod
+      - ls -ld /opt/drone/cache/go-build
+      - go env GOMODCACHE
+      - go env GOCACHE
+      - touch /opt/drone/cache/go-mod/testfile_from_build
 
   - name: rebuild cache
     image: drillster/drone-volume-cache