implement DNS resolver with memory cache feature #15

example/config.json

@@ -21,6 +21,14 @@
             }
         }
     },
+    "memcached":
+    {
+        "server":
+        {
+            "host":"127.0.0.1",
+            "port":11211
+        }
+    },
     "gui":
     {
         "pagination":
@@ -117,7 +125,42 @@
                 "connection":
                 {
                     "timeout":3,
-                    "length":10485760
+                    "length":10485760,
+                    "options":
+                    {
+                        "ssl":
+                        {
+                            "verify_peer": false,
+                            "verify_peer_name": false
+                        }
+                    }
+                },
+                "resolver":
+                {
+                    "enabled":true,
+                    "providers":
+                    [
+                        "1.1.1.1",
+                        "8.8.8.8"
+                    ],
+                    "records":
+                    [
+                        "A",
+                        "AAAA"
+                    ],
+                    "connection":
+                    {
+                        "timeout":5,
+                        "delay":60
+                    },
+                    "result":
+                    {
+                        "shuffle":false,
+                        "cache":
+                        {
+                            "timeout":3600
+                        }
+                    }
                 },
                 "queue":
                 {