func Dial(ctx context.Context, protocol, addr string) (*Conn, error) {
	conn, err := net.Dial(protocol, addr)
	if err != nil {
		return nil, err
	}
	return &Conn{conn}, nil
}
func Dial(ctx context.Context, protocol, addr string) (*Conn, error) {
	conn, err := net.Dial(protocol, addr)
	if err != nil {
		return nil, err
	}
	return &Conn{conn}, nil
}
// Dial connects to the address addr on the network protocol.
// The address format is host:port, where host may be a hostname or an IP address.
// Known protocols are "tcp" and "udp".
// The returned connection satisfies net.Conn, and is valid while ctx is valid;
// if the connection is to be used after ctx becomes invalid, invoke SetContext
// with the new context.