Update README.md

[sebastianpiskorski]

I could not run bo build without running go mod init. I'm not a Go developer, so I do not understand it fully and errors displayed did not explain anything that I could understand.

Error message:

main.go:12:2: /home/user/go/src/vendor/github.com/sirupsen/logrus must be imported as github.com/sirupsen/logrus
../../model/reader.go:9:2: cannot find package "." in:
	/home/user/go/src/vendor/github.com/sirupsen/logrus
main.go:13:2: cannot find package "." in:
	/home/user/go/src/gopkg.in/alecthomas/kingpin.v2