Try setting a workspace

.drone.yml

@@ -1,14 +1,15 @@
 platform: ${platform}
 
+workspace:
+  base: /go
+
 pipeline:
   build:
     image: golang:1.10
-    pull: true
     commands:
       - go version
       - go env
       - go get -u github.com/golang/dep/cmd/dep
-      # - dep ensure -vendor-only
       - make build
   publish:
     image: plugins/docker:${docker_tag}