json/call.go
func NewClient(ch *tchannel.Channel, targetService string, opts *ClientOptions) *Client {
	client := &Client{
		ch:            ch,
		targetService: targetService,
	}
	if opts != nil && opts.HostPort != "" {
		client.hostPort = opts.HostPort
	}
	return client
}
func NewClient(ch *tchannel.Channel, targetService string, opts *ClientOptions) *Client {
	client := &Client{
		ch:            ch,
		targetService: targetService,
	}
	if opts != nil && opts.HostPort != "" {
		client.hostPort = opts.HostPort
	}
	return client
}
// NewClient returns a json.Client used to make outbound JSON calls.