I am planning to use GO to build a CLI tool executed in native system shell rather than a separate shell. What packages for GO can be used for this purpose other than codegangsta/cli ?
Additionally, Is there any package to get REST API call support (such as curl) in GO?
curl has an interesting implementation in Go with astaxie/bat
Go implemented CLI cURL-like tool for humans. Bat can be used for testing, debugging, and generally interacting with HTTP servers.
That means you needs to implement your REST server in order for any curl-like tool to interact with it.
See for instance "Making a RESTful JSON API in Go".