Make no ipv4-addr on iface warn instead of error

cmd/app/main.go

@@ -59,23 +59,23 @@ func main() {
         logger.Error.Fatal(err)
     }
     if(len(addrs) == 0){
-        logger.Error.Fatal("Interface doesnt have IPv4-Adresses")
-    }
-
-    // Add the IPv6 address to the interface
-    ipv6Str := *convertIPv4ToIPv6(&ipv6Format, addrs[0].IPNet)
-    ipv6, err := netlink.ParseAddr(ipv6Str)
-    if err != nil {
-        logger.Error.Fatal(err)
-    }
-    logger.Info.Printf("Adding converted %s -> %s to interface", addrs[0].IPNet.String(), ipv6Str)
-    err = netlink.AddrAdd(netInterface, ipv6)
-    if err != nil {
-        switch {
-        case os.IsExist(err):
-            logger.Warn.Println("Address is already set on interface")
-        default:
-            logger.Error.Fatalf("Failed to set address on interface: %v", err)
+        logger.Warn.Println("Interface doesnt have IPv4-Adresses")
+    } else {
+        // Add the IPv6 address to the interface
+        ipv6Str := *convertIPv4ToIPv6(&ipv6Format, addrs[0].IPNet)
+        ipv6, err := netlink.ParseAddr(ipv6Str)
+        if err != nil {
+            logger.Error.Fatal(err)
+        }
+        logger.Info.Printf("Adding converted %s -> %s to interface", addrs[0].IPNet.String(), ipv6Str)
+        err = netlink.AddrAdd(netInterface, ipv6)
+        if err != nil {
+            switch {
+            case os.IsExist(err):
+                logger.Warn.Println("Address is already set on interface")
+            default:
+                logger.Error.Fatalf("Failed to set address on interface: %v", err)
+            }
         }
     }