diff --git a/.idea/misc.xml b/.idea/misc.xml
index 639900d13c6182e452e33a3bd638e70a0146c785..35fb8b961574e4f35fb403d856b5fab442742aed 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
-  <component name="ProjectRootManager">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_14" default="false" project-jdk-name="15" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/out" />
   </component>
 </project>
\ No newline at end of file
diff --git a/.idea/workspace.xml b/.idea/workspace.xml
index eeaa5a80aaa910283ddda98a112ec8ad63a58f4a..54c39a11e14c96af9cd86e67faadd3bfa43cf60b 100644
--- a/.idea/workspace.xml
+++ b/.idea/workspace.xml
@@ -19,26 +19,29 @@
     <select />
   </component>
   <component name="ChangeListManager">
-    <list default="true" id="d365b3bd-6b35-4929-97b9-bcb786acfffc" name="Default Changelist" comment="2021年12月21日">
+    <list default="true" id="d365b3bd-6b35-4929-97b9-bcb786acfffc" name="Default Changelist" comment="2022年1月12日">
       <change afterPath="$PROJECT_DIR$/basic/c.out" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/basic/triangle_test.go" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/errhandling/defer/defer.go" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/errhandling/filelistingserver/filelisting/filelist.go" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/errhandling/filelistingserver/web.go" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/crawler/main.go" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/errhandling/filelistingserver/errwrapper_test.go" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/errhandling/recover/recover.go" afterDir="false" />
       <change afterPath="$PROJECT_DIR$/fib.txt" afterDir="false" />
       <change afterPath="$PROJECT_DIR$/fib1.txt" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/fib3.txt" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/function/adder/main.go" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/function/fib.go" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/function/fib2.go" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/functional/fib/fib.go" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/go.sum" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/goroutine/goroutine.go" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/http/client.go" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/maze/maze.go" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/maze/maze.in" afterDir="false" />
       <change afterPath="$PROJECT_DIR$/nonrepeating/c.out" afterDir="false" />
       <change afterPath="$PROJECT_DIR$/nonrepeating/cpu.out" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/nonrepeating/nonrepeating.test" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/nonrepeating/nonrepeating_test.go" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/queue/queue_test.go" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/.idea/misc.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/misc.xml" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/workspace.xml" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/basic/basic.go" beforeDir="false" afterPath="$PROJECT_DIR$/basic/basic.go" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/nonrepeating/nonrepeating.go" beforeDir="false" afterPath="$PROJECT_DIR$/nonrepeating/nonrepeating.go" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/errhandling/filelistingserver/filelisting/filelist.go" beforeDir="false" afterPath="$PROJECT_DIR$/errhandling/filelistingserver/filelisting/filelist.go" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/errhandling/filelistingserver/web.go" beforeDir="false" afterPath="$PROJECT_DIR$/errhandling/filelistingserver/web.go" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/go.mod" beforeDir="false" afterPath="$PROJECT_DIR$/go.mod" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/nonrepeating/nonrepeating.test" beforeDir="false" afterPath="$PROJECT_DIR$/nonrepeating/nonrepeating.test" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/queue/entry/main.go" beforeDir="false" afterPath="$PROJECT_DIR$/queue/entry/main.go" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/queue/queue.go" beforeDir="false" afterPath="$PROJECT_DIR$/queue/queue.go" afterDir="false" />
     </list>
     <option name="SHOW_DIALOG" value="false" />
     <option name="HIGHLIGHT_CONFLICTS" value="true" />
@@ -48,8 +51,8 @@
   <component name="FileTemplateManagerImpl">
     <option name="RECENT_TEMPLATES">
       <list>
-        <option value="Go Application" />
         <option value="Go File" />
+        <option value="Go Application" />
       </list>
     </option>
   </component>
@@ -70,45 +73,58 @@
   </component>
   <component name="PropertiesComponent">
     <property name="ASKED_ADD_EXTERNAL_FILES" value="true" />
-    <property name="DefaultGoTemplateProperty" value="Go File" />
+    <property name="DefaultGoTemplateProperty" value="Go Application" />
     <property name="RunOnceActivity.OpenProjectViewOnStart" value="true" />
     <property name="WebServerToolWindowFactoryState" value="false" />
     <property name="aspect.path.notification.shown" value="true" />
     <property name="go.import.settings.migrated" value="true" />
     <property name="last_opened_file_path" value="$PROJECT_DIR$" />
     <property name="nodejs_package_manager_path" value="npm" />
+    <property name="project.structure.last.edited" value="Project" />
+    <property name="project.structure.proportion" value="0.0" />
+    <property name="project.structure.side.proportion" value="0.0" />
+    <property name="run.code.analysis.last.selected.profile" value="pProject Default" />
+    <property name="settings.editor.selected.configurable" value="preferences.lookFeel" />
   </component>
   <component name="RecentsManager">
+    <key name="CopyFile.RECENT_KEYS">
+      <recent name="$PROJECT_DIR$" />
+    </key>
     <key name="MoveFile.RECENT_KEYS">
+      <recent name="$PROJECT_DIR$/queue" />
       <recent name="$PROJECT_DIR$/function/adder" />
       <recent name="$PROJECT_DIR$/string" />
       <recent name="$PROJECT_DIR$/slices" />
       <recent name="$PROJECT_DIR$/sliceops" />
-      <recent name="$PROJECT_DIR$/nonrepeating" />
-    </key>
-    <key name="CopyFile.RECENT_KEYS">
-      <recent name="$PROJECT_DIR$" />
     </key>
   </component>
-  <component name="RunManager" selected="Go Test.BenchmarkDubstr in learngo/nonrepeating">
-    <configuration default="true" type="ArquillianTestNG" factoryName="" nameIsGenerated="true">
+  <component name="RunManager" selected="Go Build.go build learngo/crawler">
+    <configuration default="true" type="ArquillianJUnit" factoryName="" nameIsGenerated="true">
       <option name="arquillianRunConfiguration">
         <value>
           <option name="containerStateName" value="" />
         </value>
       </option>
-      <option name="TEST_OBJECT" value="CLASS" />
-      <properties />
-      <listeners />
+      <option name="TEST_OBJECT" value="class" />
       <method v="2">
         <option name="Make" enabled="true" />
       </method>
     </configuration>
-    <configuration name="go build defer.go" type="GoApplicationRunConfiguration" factoryName="Go Application" temporary="true" nameIsGenerated="true">
+    <configuration default="true" type="GoApplicationRunConfiguration" factoryName="Go Application">
       <module name="learngo" />
       <working_directory value="$PROJECT_DIR$" />
+      <go_parameters value="-i" />
       <kind value="FILE" />
-      <filePath value="$PROJECT_DIR$/errhandling/defer/defer.go" />
+      <filePath value="$PROJECT_DIR$" />
+      <directory value="$PROJECT_DIR$" />
+      <method v="2" />
+    </configuration>
+    <configuration name="go build learngo/crawler" type="GoApplicationRunConfiguration" factoryName="Go Application" temporary="true" nameIsGenerated="true">
+      <module name="learngo" />
+      <working_directory value="$PROJECT_DIR$" />
+      <kind value="PACKAGE" />
+      <filePath value="$PROJECT_DIR$/crawler/main.go" />
+      <package value="learngo/crawler" />
       <directory value="$PROJECT_DIR$" />
       <method v="2" />
     </configuration>
@@ -121,46 +137,50 @@
       <directory value="$PROJECT_DIR$" />
       <method v="2" />
     </configuration>
-    <configuration name="BenchmarkDubstr in learngo/nonrepeating" type="GoTestRunConfiguration" factoryName="Go Test" temporary="true" nameIsGenerated="true">
+    <configuration name="go build learngo/http" type="GoApplicationRunConfiguration" factoryName="Go Application" temporary="true" nameIsGenerated="true">
       <module name="learngo" />
-      <working_directory value="$PROJECT_DIR$/nonrepeating" />
-      <framework value="gobench" />
+      <working_directory value="$PROJECT_DIR$" />
       <kind value="PACKAGE" />
-      <package value="learngo/nonrepeating" />
+      <filePath value="$PROJECT_DIR$/http/client.go" />
+      <package value="learngo/http" />
       <directory value="$PROJECT_DIR$" />
-      <filePath value="$PROJECT_DIR$" />
-      <pattern value="^\QBenchmarkDubstr\E$" />
       <method v="2" />
     </configuration>
-    <configuration name="TestSubstr in learngo/nonrepeating" type="GoTestRunConfiguration" factoryName="Go Test" temporary="true" nameIsGenerated="true">
+    <configuration name="go build learngo/maze" type="GoApplicationRunConfiguration" factoryName="Go Application" temporary="true" nameIsGenerated="true">
       <module name="learngo" />
-      <working_directory value="$PROJECT_DIR$/nonrepeating" />
-      <framework value="gotest" />
+      <working_directory value="$PROJECT_DIR$" />
       <kind value="PACKAGE" />
-      <package value="learngo/nonrepeating" />
+      <filePath value="$PROJECT_DIR$/maze/maze.go" />
+      <package value="learngo/maze" />
+      <directory value="$PROJECT_DIR$" />
+      <method v="2" />
+    </configuration>
+    <configuration name="go build web.go" type="GoApplicationRunConfiguration" factoryName="Go Application" temporary="true" nameIsGenerated="true">
+      <module name="learngo" />
+      <working_directory value="$PROJECT_DIR$" />
+      <kind value="FILE" />
+      <filePath value="$PROJECT_DIR$/errhandling/filelistingserver/web.go" />
+      <package value="learngo" />
       <directory value="$PROJECT_DIR$" />
-      <filePath value="$PROJECT_DIR$" />
-      <pattern value="^\QTestSubstr\E$" />
       <method v="2" />
     </configuration>
-    <configuration name="TestTriangle in learngo/basic" type="GoTestRunConfiguration" factoryName="Go Test" temporary="true" nameIsGenerated="true">
+    <configuration default="true" type="GoTestRunConfiguration" factoryName="Go Test">
       <module name="learngo" />
-      <working_directory value="$PROJECT_DIR$/basic" />
+      <working_directory value="$PROJECT_DIR$" />
+      <go_parameters value="-i" />
       <framework value="gotest" />
-      <kind value="PACKAGE" />
-      <package value="learngo/basic" />
+      <kind value="DIRECTORY" />
       <directory value="$PROJECT_DIR$" />
       <filePath value="$PROJECT_DIR$" />
-      <pattern value="^\QTestTriangle\E$" />
       <method v="2" />
     </configuration>
     <recent_temporary>
       <list>
-        <item itemvalue="Go Test.BenchmarkDubstr in learngo/nonrepeating" />
-        <item itemvalue="Go Test.TestSubstr in learngo/nonrepeating" />
-        <item itemvalue="Go Test.TestTriangle in learngo/basic" />
+        <item itemvalue="Go Build.go build learngo/crawler" />
+        <item itemvalue="Go Build.go build web.go" />
         <item itemvalue="Go Build.go build learngo/errhandling/filelistingserver" />
-        <item itemvalue="Go Build.go build defer.go" />
+        <item itemvalue="Go Build.go build learngo/http" />
+        <item itemvalue="Go Build.go build learngo/maze" />
       </list>
     </recent_temporary>
   </component>
@@ -215,7 +235,25 @@
       <workItem from="1641829903332" duration="1606000" />
       <workItem from="1641831706808" duration="1211000" />
       <workItem from="1642001770539" duration="1820000" />
-      <workItem from="1642003643024" duration="282000" />
+      <workItem from="1642003643024" duration="751000" />
+      <workItem from="1642086117732" duration="518000" />
+      <workItem from="1642305749024" duration="374000" />
+      <workItem from="1642329370739" duration="1708000" />
+      <workItem from="1642331483597" duration="1846000" />
+      <workItem from="1642333755980" duration="1542000" />
+      <workItem from="1646924817791" duration="1698000" />
+      <workItem from="1646926631154" duration="1537000" />
+      <workItem from="1646928721724" duration="1317000" />
+      <workItem from="1657030333952" duration="1615000" />
+      <workItem from="1657032143579" duration="1260000" />
+      <workItem from="1657034026468" duration="1465000" />
+      <workItem from="1657035905215" duration="1052000" />
+      <workItem from="1657637090930" duration="512000" />
+      <workItem from="1657639674570" duration="1702000" />
+      <workItem from="1657641499807" duration="1126000" />
+      <workItem from="1657814506188" duration="1509000" />
+      <workItem from="1657816118798" duration="314000" />
+      <workItem from="1658072272414" duration="533000" />
     </task>
     <task id="LOCAL-00001" summary="2021年12月5日">
       <created>1638720681912</created>
@@ -301,7 +339,21 @@
       <option name="project" value="LOCAL" />
       <updated>1640103197749</updated>
     </task>
-    <option name="localTasksCounter" value="13" />
+    <task id="LOCAL-00013" summary="2022年1月12日">
+      <created>1642004006795</created>
+      <option name="number" value="00013" />
+      <option name="presentableId" value="LOCAL-00013" />
+      <option name="project" value="LOCAL" />
+      <updated>1642004006795</updated>
+    </task>
+    <task id="LOCAL-00014" summary="2022年1月12日">
+      <created>1642004021802</created>
+      <option name="number" value="00014" />
+      <option name="presentableId" value="LOCAL-00014" />
+      <option name="project" value="LOCAL" />
+      <updated>1642004021802</updated>
+    </task>
+    <option name="localTasksCounter" value="15" />
     <servers />
   </component>
   <component name="TypeScriptGeneratedFilesManager">
@@ -328,7 +380,8 @@
     <MESSAGE value="2021年12月11日" />
     <MESSAGE value="2021年12月13日" />
     <MESSAGE value="2021年12月21日" />
-    <option name="LAST_COMMIT_MESSAGE" value="2021年12月21日" />
+    <MESSAGE value="2022年1月12日" />
+    <option name="LAST_COMMIT_MESSAGE" value="2022年1月12日" />
   </component>
   <component name="VgoProject">
     <integration-enabled>true</integration-enabled>
@@ -340,103 +393,64 @@
     </environment>
   </component>
   <component name="WindowStateProjectService">
-    <state x="1647" y="58" key="#Inspections" timestamp="1638623871165">
-      <screen x="1366" y="-158" width="1859" height="1055" />
-    </state>
-    <state x="1647" y="58" key="#Inspections/1366.-158.1859.1055/0.25.1366.743@1366.-158.1859.1055" timestamp="1638623871165" />
-    <state x="-1496" y="-10" key="#com.intellij.execution.impl.EditConfigurationsDialog" timestamp="1638463705929">
-      <screen x="-1920" y="-196" width="1920" height="1055" />
+    <state x="2032" y="250" key="#com.intellij.fileTypes.FileTypeChooser" timestamp="1657030417371">
+      <screen x="1366" y="-83" width="1859" height="1055" />
     </state>
-    <state x="-1496" y="-10" key="#com.intellij.execution.impl.EditConfigurationsDialog/-1920.-196.1920.1055/0.25.1311.743@-1920.-196.1920.1055" timestamp="1638463705929" />
-    <state x="496" y="116" key="#com.intellij.ide.util.MemberChooser" timestamp="1640013650164">
-      <screen x="0" y="25" width="1366" height="743" />
+    <state x="2032" y="250" key="#com.intellij.fileTypes.FileTypeChooser/1366.-83.1859.1055/0.25.1366.743@1366.-83.1859.1055" timestamp="1657030417371" />
+    <state x="2044" y="303" key="ANALYSIS_DLG_com.intellij.analysis.BaseAnalysisAction$1" timestamp="1657035246305">
+      <screen x="1366" y="-83" width="1859" height="1055" />
     </state>
-    <state x="496" y="116" key="#com.intellij.ide.util.MemberChooser/1366.-158.1860.1055/0.25.1366.743@0.25.1366.743" timestamp="1640013650164" />
-    <state width="461" height="466" key="DebuggerActiveHint" timestamp="1641390841146">
-      <screen x="0" y="25" width="1366" height="743" />
+    <state x="2044" y="303" key="ANALYSIS_DLG_com.intellij.analysis.BaseAnalysisAction$1/1366.-83.1859.1055/0.25.1366.743@1366.-83.1859.1055" timestamp="1657035246305" />
+    <state width="1878" height="453" key="GridCell.Tab.0.bottom" timestamp="1658073933116">
+      <screen x="1366" y="-83" width="1920" height="1055" />
     </state>
-    <state width="461" height="466" key="DebuggerActiveHint/1366.-158.1859.1055/0.25.1366.743@0.25.1366.743" timestamp="1641390841146" />
-    <state width="1324" height="368" key="GridCell.Tab.0.bottom" timestamp="1642002110745">
-      <screen x="0" y="0" width="1366" height="768" />
+    <state width="1878" height="479" key="GridCell.Tab.0.bottom/1366.-108.1920.1080/0.25.1366.743@1366.-108.1920.1080" timestamp="1657640002468" />
+    <state width="1817" height="540" key="GridCell.Tab.0.bottom/1366.-83.1859.1055/0.25.1366.743@1366.-83.1859.1055" timestamp="1657640638737" />
+    <state width="1878" height="453" key="GridCell.Tab.0.bottom/1366.-83.1920.1055/0.25.1366.743@1366.-83.1920.1055" timestamp="1658073933116" />
+    <state width="1878" height="453" key="GridCell.Tab.0.center" timestamp="1658073933113">
+      <screen x="1366" y="-83" width="1920" height="1055" />
     </state>
-    <state width="1324" height="282" key="GridCell.Tab.0.bottom/-1920.-171.1920.1055/0.0.1308.768@0.0.1308.768" timestamp="1641832930610" />
-    <state width="1266" height="261" key="GridCell.Tab.0.bottom/-1920.-171.1920.1055/0.25.1308.743@0.25.1308.743" timestamp="1641831352122" />
-    <state width="1878" height="455" key="GridCell.Tab.0.bottom/-1920.-196.1920.1055/0.25.1311.743@-1920.-196.1920.1055" timestamp="1638463841375" />
-    <state width="1324" height="368" key="GridCell.Tab.0.bottom/-1920.-196.1920.1080/0.0.1366.768@0.0.1366.768" timestamp="1642002110745" />
-    <state width="1324" height="313" key="GridCell.Tab.0.bottom/1366.-158.1859.1055/0.25.1366.743@0.25.1366.743" timestamp="1641395611308" />
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-    <state width="1324" height="199" key="GridCell.Tab.0.bottom/1366.-158.1860.1055/0.25.1366.743@0.25.1366.743" timestamp="1640014417559" />
-    <state width="1324" height="271" key="GridCell.Tab.0.bottom/1366.-183.1920.1080/0.0.1366.768@0.0.1366.768" timestamp="1639499455426" />
-    <state width="1324" height="368" key="GridCell.Tab.0.center" timestamp="1642002110742">
-      <screen x="0" y="0" width="1366" height="768" />
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+    <state width="1817" height="540" key="GridCell.Tab.0.center/1366.-83.1859.1055/0.25.1366.743@1366.-83.1859.1055" timestamp="1657640638735" />
+    <state width="1878" height="453" key="GridCell.Tab.0.center/1366.-83.1920.1055/0.25.1366.743@1366.-83.1920.1055" timestamp="1658073933113" />
+    <state width="1878" height="453" key="GridCell.Tab.0.left" timestamp="1658073933109">
+      <screen x="1366" y="-83" width="1920" height="1055" />
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-    <state width="1324" height="368" key="GridCell.Tab.0.left" timestamp="1642002110741">
-      <screen x="0" y="0" width="1366" height="768" />
+    <state width="1878" height="479" key="GridCell.Tab.0.left/1366.-108.1920.1080/0.25.1366.743@1366.-108.1920.1080" timestamp="1657640002464" />
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+    <state width="1878" height="453" key="GridCell.Tab.0.right" timestamp="1658073933114">
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\ No newline at end of file