synchronize get_access_token

lib/weixin_authorize/client.rb

 # encoding: utf-8
+require "monitor"
 require "redis"
 require 'digest/md5'
 module WeixinAuthorize
 
   class Client
+
+    include MonitorMixin
+
     include Api::User
     include Api::Menu
     include Api::Custom
@@ -26,12 +30,13 @@ module WeixinAuthorize
       @redis_key = security_redis_key(options[:redis_key] || "weixin_#{app_id}")
       @jsticket_redis_key = security_redis_key("js_sdk_#{app_id}")
       @custom_access_token = options[:custom_access_token]
+      super() # Monitor#initialize
     end
 
     # return token
     def get_access_token
       return custom_access_token if !custom_access_token.nil?
-      token_store.access_token
+      synchronize{ token_store.access_token }
     end
 
     # 检查appid和app_secret是否有效。