Got error pq: syntax error at the end of ... when doing custom dialer

[QuangTung97]

I tried to do custom dialing using this example:
#470 (comment)

type drvWrapper struct{}

type customDialer struct{}

func (d *drvWrapper) Open(name string) (driver.Conn, error) {
	return pq.DialOpen(customDialer{}, name)
}

func (customDialer) Dial(network, address string) (net.Conn, error) {
	return net.Dial(network, address)
}

func (customDialer) DialTimeout(network, address string, timeout time.Duration) (net.Conn, error) {
	return net.DialTimeout(network, address, timeout)
}

func init() {
	sql.Register("mypq", &drvWrapper{})
}

And then create a DB through sqlx:

	db := sqlx.MustOpen("mypq", "postgres://"+cfg.Postgres.DSN())

I encountered this error: "pq: syntax error at end of input"

But when I switched back the default driver name:

	db := sqlx.MustOpen("postgres", "postgres://"+cfg.Postgres.DSN())

The error immediately went away.
Could anyone help me point out the problem? Thanks