StatusCode extract the status code if the error implements Coder interface.

arrived at last page, fetch is Completed.

 All results were fetched.

fetching next page Failed.

auto fetch was Paused.

Results are not available yet.

auto fetch is Running.

More results are available (pagination).

Custom Internal type that shall be used internally by the client.

Interface for the jsonrpc2 conn struct here https://github.com/sourcegraph/jsonrpc2/blob/master/conn.go.