diff --git a/.idea/workspace.xml b/.idea/workspace.xml
index b38d169..6ca1bfa 100644
--- a/.idea/workspace.xml
+++ b/.idea/workspace.xml
@@ -6,13 +6,8 @@
   <component name="ChangeListManager">
     <list default="true" readonly="true" id="03ed5703-81a1-441b-849c-c426276586b7" name="Default" comment="">
       <change beforePath="$PROJECT_DIR$/.idea/workspace.xml" afterPath="$PROJECT_DIR$/.idea/workspace.xml" />
-      <change beforePath="$PROJECT_DIR$/cache/cache_redis.go" afterPath="$PROJECT_DIR$/cache/cache_redis.go" />
-      <change beforePath="$PROJECT_DIR$/cache_db.go" afterPath="$PROJECT_DIR$/cache_db.go" />
-      <change beforePath="$PROJECT_DIR$/cache_memory.go" afterPath="$PROJECT_DIR$/cache_memory.go" />
       <change beforePath="$PROJECT_DIR$/db.go" afterPath="$PROJECT_DIR$/db.go" />
       <change beforePath="$PROJECT_DIR$/example/main.go" afterPath="$PROJECT_DIR$/example/main.go" />
-      <change beforePath="$PROJECT_DIR$/obj.go" afterPath="$PROJECT_DIR$/obj.go" />
-      <change beforePath="$PROJECT_DIR$/objtoobj.go" afterPath="$PROJECT_DIR$/objtoobj.go" />
     </list>
     <ignored path=".idea/dataSources.local.xml" />
     <option name="EXCLUDED_CONVERTED_TO_IGNORED" value="true" />
@@ -30,13 +25,13 @@
   </component>
   <component name="FileEditorManager">
     <leaf SIDE_TABS_SIZE_LIMIT_KEY="300">
-      <file leaf-file-name="main.go" pinned="false" current-in-tab="true">
+      <file leaf-file-name="main.go" pinned="false" current-in-tab="false">
         <entry file="file://$PROJECT_DIR$/example/main.go">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="220">
-              <caret line="88" column="43" lean-forward="true" selection-start-line="88" selection-start-column="43" selection-end-line="88" selection-end-column="43" />
+            <state relative-caret-position="165">
+              <caret line="11" column="1" lean-forward="true" selection-start-line="11" selection-start-column="1" selection-end-line="11" selection-end-column="1" />
               <folding>
-                <element signature="e#14#207#0" expanded="true" />
+                <element signature="e#14#209#0" expanded="true" />
               </folding>
             </state>
           </provider>
@@ -84,11 +79,11 @@
           </provider>
         </entry>
       </file>
-      <file leaf-file-name="db.go" pinned="false" current-in-tab="false">
+      <file leaf-file-name="db.go" pinned="false" current-in-tab="true">
         <entry file="file://$PROJECT_DIR$/db.go">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="370">
-              <caret line="893" column="9" lean-forward="true" selection-start-line="893" selection-start-column="9" selection-end-line="893" selection-end-column="9" />
+            <state relative-caret-position="120">
+              <caret line="8" column="13" lean-forward="false" selection-start-line="8" selection-start-column="13" selection-end-line="8" selection-end-column="13" />
               <folding />
             </state>
           </provider>
@@ -205,8 +200,8 @@
         <option value="$PROJECT_DIR$/cache_memory.go" />
         <option value="$PROJECT_DIR$/cache_db.go" />
         <option value="$PROJECT_DIR$/cache/cache_redis.go" />
-        <option value="$PROJECT_DIR$/db.go" />
         <option value="$PROJECT_DIR$/example/main.go" />
+        <option value="$PROJECT_DIR$/db.go" />
       </list>
     </option>
   </component>
@@ -483,7 +478,7 @@
       <workItem from="1522778659126" duration="455000" />
       <workItem from="1522779789231" duration="6991000" />
       <workItem from="1523202491878" duration="853000" />
-      <workItem from="1523288830673" duration="5049000" />
+      <workItem from="1523288830673" duration="5111000" />
     </task>
     <task id="LOCAL-00001">
       <created>1500458878821</created>
@@ -688,11 +683,18 @@
       <option name="project" value="LOCAL" />
       <updated>1523203335093</updated>
     </task>
-    <option name="localTasksCounter" value="30" />
+    <task id="LOCAL-00030" summary="数据库缓存更新">
+      <created>1523294190912</created>
+      <option name="number" value="00030" />
+      <option name="presentableId" value="LOCAL-00030" />
+      <option name="project" value="LOCAL" />
+      <updated>1523294190912</updated>
+    </task>
+    <option name="localTasksCounter" value="31" />
     <servers />
   </component>
   <component name="TimeTrackingManager">
-    <option name="totallyTimeSpent" value="106572000" />
+    <option name="totallyTimeSpent" value="106634000" />
   </component>
   <component name="TodoView">
     <todo-panel id="selected-file">
@@ -713,7 +715,7 @@
       <window_info id="Capture Analysis" active="false" anchor="right" auto_hide="false" internal_type="DOCKED" type="DOCKED" visible="false" show_stripe_button="true" weight="0.33" sideWeight="0.5" order="3" side_tool="false" content_ui="tabs" />
       <window_info id="Event Log" active="false" anchor="bottom" auto_hide="false" internal_type="DOCKED" type="DOCKED" visible="false" show_stripe_button="true" weight="0.33" sideWeight="0.5" order="7" side_tool="true" content_ui="tabs" />
       <window_info id="Maven Projects" active="false" anchor="right" auto_hide="false" internal_type="DOCKED" type="DOCKED" visible="false" show_stripe_button="true" weight="0.33" sideWeight="0.5" order="3" side_tool="false" content_ui="tabs" />
-      <window_info id="Run" active="false" anchor="bottom" auto_hide="false" internal_type="DOCKED" type="DOCKED" visible="true" show_stripe_button="true" weight="0.328125" sideWeight="0.5" order="2" side_tool="false" content_ui="tabs" />
+      <window_info id="Run" active="true" anchor="bottom" auto_hide="false" internal_type="DOCKED" type="DOCKED" visible="true" show_stripe_button="true" weight="0.328125" sideWeight="0.5" order="2" side_tool="false" content_ui="tabs" />
       <window_info id="Version Control" active="false" anchor="bottom" auto_hide="false" internal_type="DOCKED" type="DOCKED" visible="false" show_stripe_button="true" weight="0.6322917" sideWeight="0.5" order="7" side_tool="false" content_ui="tabs" />
       <window_info id="Terminal" active="false" anchor="bottom" auto_hide="false" internal_type="DOCKED" type="DOCKED" visible="false" show_stripe_button="true" weight="0.32805908" sideWeight="0.5" order="7" side_tool="false" content_ui="tabs" />
       <window_info id="Capture Tool" active="false" anchor="left" auto_hide="false" internal_type="DOCKED" type="DOCKED" visible="false" show_stripe_button="true" weight="0.33" sideWeight="0.5" order="2" side_tool="false" content_ui="tabs" />
@@ -748,7 +750,8 @@
     <MESSAGE value="demo" />
     <MESSAGE value="管理端初步" />
     <MESSAGE value="工具" />
-    <option name="LAST_COMMIT_MESSAGE" value="工具" />
+    <MESSAGE value="数据库缓存更新" />
+    <option name="LAST_COMMIT_MESSAGE" value="数据库缓存更新" />
   </component>
   <component name="XDebuggerManager">
     <breakpoint-manager>
@@ -762,7 +765,7 @@
         <state relative-caret-position="0">
           <caret line="0" column="0" lean-forward="false" selection-start-line="0" selection-start-column="0" selection-end-line="0" selection-end-column="0" />
           <folding>
-            <element signature="e#14#207#0" expanded="true" />
+            <element signature="e#14#209#0" expanded="true" />
           </folding>
         </state>
       </provider>
@@ -846,7 +849,7 @@
         <state relative-caret-position="0">
           <caret line="0" column="0" lean-forward="false" selection-start-line="0" selection-start-column="0" selection-end-line="0" selection-end-column="0" />
           <folding>
-            <element signature="e#14#207#0" expanded="true" />
+            <element signature="e#14#209#0" expanded="true" />
           </folding>
         </state>
       </provider>
@@ -929,7 +932,7 @@
         <state relative-caret-position="270">
           <caret line="18" column="29" lean-forward="false" selection-start-line="18" selection-start-column="29" selection-end-line="18" selection-end-column="29" />
           <folding>
-            <element signature="e#14#207#0" expanded="true" />
+            <element signature="e#14#209#0" expanded="true" />
           </folding>
         </state>
       </provider>
@@ -947,7 +950,7 @@
         <state relative-caret-position="0">
           <caret line="0" column="0" lean-forward="false" selection-start-line="0" selection-start-column="0" selection-end-line="0" selection-end-column="0" />
           <folding>
-            <element signature="e#14#207#0" expanded="true" />
+            <element signature="e#14#209#0" expanded="true" />
           </folding>
         </state>
       </provider>
@@ -1058,14 +1061,6 @@
         </state>
       </provider>
     </entry>
-    <entry file="file://$PROJECT_DIR$/db.go">
-      <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="370">
-          <caret line="893" column="9" lean-forward="true" selection-start-line="893" selection-start-column="9" selection-end-line="893" selection-end-column="9" />
-          <folding />
-        </state>
-      </provider>
-    </entry>
     <entry file="file://$PROJECT_DIR$/cache_db.go">
       <provider selected="true" editor-type-id="text-editor">
         <state relative-caret-position="281">
@@ -1076,13 +1071,21 @@
     </entry>
     <entry file="file://$PROJECT_DIR$/example/main.go">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="220">
-          <caret line="88" column="43" lean-forward="true" selection-start-line="88" selection-start-column="43" selection-end-line="88" selection-end-column="43" />
+        <state relative-caret-position="165">
+          <caret line="11" column="1" lean-forward="true" selection-start-line="11" selection-start-column="1" selection-end-line="11" selection-end-column="1" />
           <folding>
-            <element signature="e#14#207#0" expanded="true" />
+            <element signature="e#14#209#0" expanded="true" />
           </folding>
         </state>
       </provider>
     </entry>
+    <entry file="file://$PROJECT_DIR$/db.go">
+      <provider selected="true" editor-type-id="text-editor">
+        <state relative-caret-position="120">
+          <caret line="8" column="13" lean-forward="false" selection-start-line="8" selection-start-column="13" selection-end-line="8" selection-end-column="13" />
+          <folding />
+        </state>
+      </provider>
+    </entry>
   </component>
 </project>
\ No newline at end of file
diff --git a/db.go b/db.go
index 8f819e1..b139dd1 100644
--- a/db.go
+++ b/db.go
@@ -7,7 +7,6 @@ import (
 	"os"
 	"reflect"
 	"strings"
-	"sync"
 )
 
 type HoTimeDB struct {
diff --git a/example/main.go b/example/main.go
index b500685..dc4ee6c 100644
--- a/example/main.go
+++ b/example/main.go
@@ -8,7 +8,7 @@ import (
 	//"go.hoteas.com/hotime/cache"
 	"golang.org/x/net/websocket"
 	"time"
-	"go.hoteas.com/hotime/cache"
+	//"go.hoteas.com/hotime/cache"
 )
 
 func main() {