[solved]"make test" fails for "import cycle not allowed"

By following the “Developer Machine Setup” (https://docs.mattermost.com/developer/developer-setup.html#ubuntu) , I run into a error as following image attachment.Can you help me?

After waiting for 1 hour, There is no help coming makes me realize that I may have made low-level mistakes. It turns out is true.
I set both my GOPATH and GOROOT to the location where Go installed out of ignorance.
GOPATH should be where projects are (a “workspace”), not where go is installed.