m = make(map[string]int)
			services[netw] = m
		}
		for i := 0; i < len(f); i++ {
			if i != 1 { // f[1] was port/net
				m[f[i]] = port
			}
		}
	}
}

// goLookupPort is the native Go implementation of LookupPort.
func goLookupPort(network, service string) (port int, err error) {
	onceReadServices.Do(readServices)
	return lookupPortMap(network, service)

		if err != nil {
			// Issue 18213: if cgo fails, first check to see whether we
			// have the answer baked-in to the net package.
			if port, err := goLookupPort(network, service); err == nil {
				return port, nil
			}
		}
		return port, err
	}
	return goLookupPort(network, service)
}

func (r *Resolver) lookupCNAME(ctx context.Context, name string) (string, error) {
	order, conf := systemConf().hostLookupOrder(r, name)

// numbers for platforms that don't have a complete list of port numbers.
//
// See https://www.iana.org/assignments/service-names-port-numbers
//
// On Unix, this map is augmented by readServices via goLookupPort.
var services = map[string]map[string]int{
	"udp": {
		"domain": 53,
	},
	"tcp": {
		"ftp":         21,
		"ftps":        990,
		"gopher":      70, // ʕ◔ϖ◔ʔ
		"http":        80,
		"https":       443,