coinbase.go
func (c Client) Get(path string, params interface{}, holder interface{}) error {
	return c.rpc.Request("GET", path, params, &holder)
}
func (c Client) Get(path string, params interface{}, holder interface{}) error {
	return c.rpc.Request("GET", path, params, &holder)
}
// Get sends a GET request and marshals response data into holder