CloseableHttpAsyncClient异步请求失败后无法关闭

    所用版本asyncclient 4.1
    代码： public static void main(String[] args) {
a();
}
public static void a(){

 final CloseableHttpAsyncClient httpclient = ab();
String url ;    
url="http://ww1w1.ffefdfdfdsdasdsdbafgfidugfligffdgfgee.com";           
try {
httpclient.start();
HttpGet put=new HttpGet(url);
put.setHeader("Connection", "close"); 
httpclient.execute(put,
new FutureCallback<HttpResponse>() {     
public void completed(final HttpResponse result) {
System.out.println("1!");
try {
httpclient.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("11");
}
public void failed(final Exception ex) {
System.out.println("2");
try { 
httpclient.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(5);
}
public void cancelled() {

System.out.println(3);
}
});

} catch (Exception ex) {
System.out.println("AAAAAAAAAAAsss");
try {
httpclient.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static CloseableHttpAsyncClient ab()
{
RequestConfig requestConfig = RequestConfig.custom()
     .setConnectTimeout(100)
     .setConnectionRequestTimeout(100)
     .setSocketTimeout(1000)
     //.setAuthenticationEnabled(false)
     .build();
        CloseableHttpAsyncClient httpclient = HttpAsyncClients.custom()
         .setDefaultRequestConfig(requestConfig)
         .build();
        return httpclient;
}当返回时 failed时  请求无法关闭    断点走到httpclient.close()  时卡住    有知道是怎么回事的吗