scrape/manager.go
func getFqdn() (string, error) {
	hostname, err := os.Hostname()
	if err != nil {
		return "", err
	}

	ips, err := net.LookupIP(hostname)
	if err != nil {
		// Return the system hostname if we can't look up the IP address.
		return hostname, nil
	}

	lookup := func(ipStr encoding.TextMarshaler) (string, error) {
		ip, err := ipStr.MarshalText()
		if err != nil {
			return "", err
		}
		hosts, err := net.LookupAddr(string(ip))
		if err != nil || len(hosts) == 0 {
			return "", err
		}
		return hosts[0], nil
	}

	for _, addr := range ips {
		if ip := addr.To4(); ip != nil {
			if fqdn, err := lookup(ip); err == nil {
				return fqdn, nil
			}

		}

		if ip := addr.To16(); ip != nil {
			if fqdn, err := lookup(ip); err == nil {
				return fqdn, nil
			}

		}
	}
	return hostname, nil
}
func getFqdn() (string, error) {
	hostname, err := os.Hostname()
	if err != nil {
		return "", err
	}

	ips, err := net.LookupIP(hostname)
	if err != nil {
		// Return the system hostname if we can't look up the IP address.
		return hostname, nil
	}

	lookup := func(ipStr encoding.TextMarshaler) (string, error) {
		ip, err := ipStr.MarshalText()
		if err != nil {
			return "", err
		}
		hosts, err := net.LookupAddr(string(ip))
		if err != nil || len(hosts) == 0 {
			return "", err
		}
		return hosts[0], nil
	}

	for _, addr := range ips {
		if ip := addr.To4(); ip != nil {
			if fqdn, err := lookup(ip); err == nil {
				return fqdn, nil
			}

		}

		if ip := addr.To16(); ip != nil {
			if fqdn, err := lookup(ip); err == nil {
				return fqdn, nil
			}

		}
	}
	return hostname, nil
}
// getFqdn returns a FQDN if it's possible, otherwise falls back to hostname.