diff --git a/History.md b/History.md
index 579c573..29562b8 100644
--- a/History.md
+++ b/History.md
@@ -1,3 +1,7 @@
+1.8.20 / 2021-06-08
+==================
+  * support stateful async invocation
+
 1.8.18 / 2021-04-19
 ==================
   * add instance metrics support
diff --git a/README.md b/README.md
index 5957f74..b843463 100644
--- a/README.md
+++ b/README.md
@@ -25,7 +25,7 @@ Add Maven dependencies into pom.xml
 <dependency>
     <groupId>com.aliyun</groupId>
     <artifactId>aliyun-java-sdk-fc</artifactId>
-    <version>1.8.19</version>
+    <version>1.8.20</version>
 </dependency>
 ```
 
diff --git a/pom.xml b/pom.xml
index 4fc7c4b..852677d 100755
--- a/pom.xml
+++ b/pom.xml
@@ -5,7 +5,7 @@
     <groupId>com.aliyun</groupId>
     <artifactId>aliyun-java-sdk-fc</artifactId>
     <packaging>jar</packaging>
-    <version>1.8.19</version>
+    <version>1.8.20</version>
     <name>aliyun-java-sdk-fc</name>
     <url>https://www.aliyun.com/product/fc</url>
     <description>Aliyun Java SDK for FunctionCompute</description>
diff --git a/src/main/java/com/aliyuncs/fc/model/AsyncConfig.java b/src/main/java/com/aliyuncs/fc/model/AsyncConfig.java
index 8d48a0d..6c7953f 100644
--- a/src/main/java/com/aliyuncs/fc/model/AsyncConfig.java
+++ b/src/main/java/com/aliyuncs/fc/model/AsyncConfig.java
@@ -1,7 +1,6 @@
 package com.aliyuncs.fc.model;
 
 import com.google.gson.annotations.SerializedName;
-import com.sun.org.apache.xpath.internal.operations.Bool;
 import lombok.Data;
 
 /**