Go Client Documentation Obsolete

[tomatopeel]

https://github.com/dgraph-io/dgraph/blob/master/client/doc.go is now broken following 26ec2ac#diff-1cd41a2611da49ce63630d5a51bd82c5 though updated working code seems to be written in examples_test.go

[tomatopeel]

Pawan's updated the Go client docs to use the latest release rather than master