diff --git a/__wasm/wit-bindgen-sample/container/src/fn_fetch.rs b/__wasm/wit-bindgen-sample/container/src/fn_fetch.rs
index d7ec35f..891b12c 100644
--- a/__wasm/wit-bindgen-sample/container/src/fn_fetch.rs
+++ b/__wasm/wit-bindgen-sample/container/src/fn_fetch.rs
@@ -49,10 +49,11 @@ pub fn do_fetch(params: &str) -> FnResult {
         let mut has_user_agent = false;
         if let Some(headers) = &options.headers {
             for (k, v) in headers {
-                if k.to_lowercase() == "user-agent" {
+                let k = k.to_lowercase();
+                if k == "user-agent" {
                     has_user_agent = true;
                 }
-                request_builder = request_builder.header(k.to_string(), v.to_string());
+                request_builder = request_builder.header(k, v.to_string());
             }
         }
         if !has_user_agent {
diff --git a/__wasm/wit-bindgen-sample/container/src/main.rs b/__wasm/wit-bindgen-sample/container/src/main.rs
index 96d1bcf..182e856 100644
--- a/__wasm/wit-bindgen-sample/container/src/main.rs
+++ b/__wasm/wit-bindgen-sample/container/src/main.rs
@@ -3,6 +3,7 @@ extern crate core;
 use anyhow::Result;
 use serde_json::Value;
 use wasmtime::{Config, Engine, Instance, Linker, Module, Store};
+use crate::fn_common::FnResult;
 
 mod fn_common;
 mod fn_fetch;
@@ -10,10 +11,16 @@ mod fn_fetch;
 wit_bindgen_wasmtime::export!("../container.wit");
 
 #[derive(Default)]
-pub struct MyContainer;
+pub struct MyContainer {
+    fetch_invoked_count: u32,
+}
 
 impl container::Container for MyContainer {
     fn fetch(&mut self, params: &str) -> String {
+        if self.fetch_invoked_count > 10 {
+            return FnResult::fail("Fetch invoke count cannot more than 10").to_json();
+        }
+        self.fetch_invoked_count += 1;
         fn_fetch::do_fetch(params).to_json()
     }
 }
@@ -30,27 +37,36 @@ fn main() -> Result<()> {
     )?;
     let a = exports.eval_javascript(&mut store, r##"
         function hi(name) { return "hi: " + name; }
-        // let a = [];
-        // a.push(fetch('https://hatter.ink/util/print_request.action'));
+        let a = [];
+        // for (let i = 0; i < 12; i++) {
+            a.push(fetch('https://hatter.ink/util/print_request.action'));
+        // }
+            a.push(fetch('https://hatter.ink/ip.action'));
+            a.push(fetch('https://hatter.ink/ip/ip.jsonp'));
+            a.push(fetch('https://hatter.ink/ip2.action'));
         // for (let i = 0; i < 3; i++) { a.push(i); }
         // a.push({
         //   id: 1, name: 'hatter'
         // });
         // a.push(hi('001'));
         // a.push(hi('002'));
-        let a = fetch('https://hatter.ink/util/print_request.action');
         JSON.stringify(a)
         // a
     "##);
     let a = a.expect("error");
-    let a: Value = serde_json::from_str(&a).expect("error");
+    let a: Value = match serde_json::from_str(&a) {
+        Ok(a) => a,
+        Err(e) => panic!("ERROR: {}", e),
+    };
     let a = match a {
         Value::String(a) => a,
-        _ => panic!("error"),
+        _ => panic!("error: {}", a),
     };
 
-    // println!(">>>>>>> {}", a);
-    let v: Value = serde_json::from_str(&a).expect("errorr");
+    let v: Value = match serde_json::from_str(&a) {
+        Ok(v) => v,
+        Err(e) => panic!("Parse json1 failed: {}, raw json:\n - {}", e, a),
+    };
     let p = serde_json::to_string_pretty(&v).expect("error");
     // println!("------- {}", v);
     println!("{}", p);