Introduce explicit config

config/global_ips.go

@@ -0,0 +1,38 @@
+package config
+
+import (
+	"io/ioutil"
+	"net"
+	"net/http"
+	"strings"
+
+	"github.com/juju/errors"
+)
+
+func getGlobalIPv4() (net.IP, error) {
+	return fetchIP("https://v4.ifconfig.co/ip")
+}
+
+func getGlobalIPv6() (net.IP, error) {
+	return fetchIP("https://v6.ifconfig.co/ip")
+}
+
+func fetchIP(url string) (net.IP, error) {
+	resp, err := http.Get(url)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	respData, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	ip := net.ParseIP(strings.TrimSpace(string(respData)))
+	if ip == nil {
+		return nil, errors.Errorf("ifconfig.co returns incorrect IP %s", resp)
+	}
+
+	return ip, nil
+}