The Dgraph server binary running in my Docker container was v0.7.7. As @pawan from Slack 
suggested, I ought to be using the master branch of the server code to be using the master Go client code, whoops D:
The Dgraph server binary running in my Docker container was v0.7.7. As @pawan from Slack suggested, I ought to be using the master branch of the server code to be using the master Go client code, whoops D: