func GenCassandra(u *URL) (string, error) {
	host, port, dbname := "localhost", "9042", strings.TrimPrefix(u.Path, "/")
	if h := hostname(u.Host); h != "" {
		host = h
	}
	if p := hostport(u.Host); p != "" {
		port = p
	}
	q := u.Query()
	// add user/pass
	if u.User != nil {
		q.Set("username", u.User.Username())
		if pass, _ := u.User.Password(); pass != "" {
			q.Set("password", pass)
		}
	}
	// add dbname
	if dbname != "" {
		q.Set("keyspace", dbname)
	}
	return host + ":" + port + genQueryOptions(q), nil
}
func GenCassandra(u *URL) (string, error) {
	host, port, dbname := "localhost", "9042", strings.TrimPrefix(u.Path, "/")
	if h := hostname(u.Host); h != "" {
		host = h
	}
	if p := hostport(u.Host); p != "" {
		port = p
	}
	q := u.Query()
	// add user/pass
	if u.User != nil {
		q.Set("username", u.User.Username())
		if pass, _ := u.User.Password(); pass != "" {
			q.Set("password", pass)
		}
	}
	// add dbname
	if dbname != "" {
		q.Set("keyspace", dbname)
	}
	return host + ":" + port + genQueryOptions(q), nil
}
// GenCassandra generates a cassandra DSN from the passed URL.