Fix installing gox when Go modules enabled

.cirrus.yml

@@ -169,13 +169,14 @@ task:
     - dpkg --add-architecture ppc64el
     - apt-get update
     - apt-get install -y gcc-multilib libcap-dev libc6-dev:i386 libcap-dev:i386 libc6-dev:armhf libcap-dev:armhf libc6-dev:arm64 libcap-dev:arm64 libc6-dev:ppc64el libcap-dev:ppc64el
-    - go get github.com/mitchellh/gox
   path_script:
     - source testdata/move_to_gopath.bash
   matrix:
     - env:
         GO111MODULE: "off"
         MODULES_NAME: " Modules Off"
+      gox_script:
+        - go get github.com/mitchellh/gox
       fetch_script:
         - go get -tags "$GOX_TAGS" -d -v -t github.com/$CIRRUS_REPO_FULL_NAME/...
         - GOOS=windows go get -tags "$GOX_TAGS" -d -v -t github.com/$CIRRUS_REPO_FULL_NAME/...
@@ -184,6 +185,8 @@ task:
         - go get -tags "$GOX_TAGS" -d -v -t github.com/$CIRRUS_REPO_FULL_NAME/...
     - env:
         MODULES_NAME: ""
+      gox_script:
+        - go install github.com/mitchellh/gox@latest
       certinject_script:
         - cd $(go env GOPATH)/src/github.com/"$CIRRUS_REPO_FULL_NAME"
         - cd ../