If the private network is available, then use the private IP to reach…

… the master from the nodes

src/kubernetes/installer.cr

@@ -380,6 +380,10 @@ class Kubernetes::Installer
   end
 
   private def api_server_ip_address
-    first_master.host_ip_address.not_nil!
+    if first_master.private_ip_address.nil?
+      first_master.public_ip_address
+    else
+      first_master.private_ip_address
+    end
   end
 end