Migrate away from govendor to go modules

[bored-engineer]

• I've read and understood the Contributing guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've searched for any related issues and avoided creating a duplicate issue.

The current README.md file describes using govendor to install the package:

Install govendor if you haven't already
go get -u github.com/kardianos/govendor

govendor is now deprecated and go modules is recommended.
It appears that a go.mod file was added in e90a1ca already.

Does the README file just need an update or is some other migration work necessary to remove the govendor pattern.