There is no shorthand as of yet for the module system, though if you already have github initialized, it will automatically fill in the module name and match it with the name of your remote repository. So, I could have typed in go mod init and it would have added the github.com/tensor-programming/go-blockchain part by itself.

rsc.io is just a set of packages that I was using. The registry for go is called go-doc: https://godoc.org/