go client install

All go code are in 1 repo, the client dir don't have go.mod. So I've to install the whole repo to use client.

Suggestion:

1. add go.mod to client sub dirs.
2. or, move client to a separate git repo.
3. update your doc about how to use, your example only have command line guide, not even how to install a client. the doc still suggest to use https://github.com/dtm-labs/client, which is out of date.