clientv3/retry.go
func RetryAuthClient(c *Client) pb.AuthClient {
	return &retryAuthClient{
		ac: pb.NewAuthClient(c.conn),
	}
}
func RetryAuthClient(c *Client) pb.AuthClient {
	return &retryAuthClient{
		ac: pb.NewAuthClient(c.conn),
	}
}
// RetryAuthClient implements a AuthClient.