diff --git a/index.js b/index.js
index 5b10bf9..399f853 100644
--- a/index.js
+++ b/index.js
@@ -3,7 +3,11 @@ const dns = require('dns')
 const util = require('util')
 
 module.exports = {
-  dn2ip: async function (host) {
+
+  /*----------------------------------------------------------------
+  * Network tools
+  ----------------------------------------------------------------*/
+  async dn2ip(host) {
     // domain name 2 ip
     if (typeof host === 'string' && host) {
       var ip = await util
@@ -18,7 +22,7 @@ module.exports = {
     }
     return null
   },
-  isPrivateIp: function (addr) {
+  isPrivateIp(addr) {
     return (
       /^(::f{4}:)?10\.([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})$/i.test(addr) ||
       /^(::f{4}:)?192\.168\.([0-9]{1,3})\.([0-9]{1,3})$/i.test(addr) ||
@@ -31,7 +35,7 @@ module.exports = {
       /^::$/.test(addr)
     )
   },
-  getMyIp: function () {
+  getMyIp() {
     var publicIp = null
     var privateIp = null
     var self = this