diff --git a/examples/server.cpp b/examples/server.cpp
index 9f88639..b010b8a 100644
--- a/examples/server.cpp
+++ b/examples/server.cpp
@@ -1,11 +1,13 @@
 #include <rest_rpc.hpp>
 using namespace rest_rpc;
 
-std::string_view echo(std::string_view str) {
-  return str;
+std::string_view echo(std::string_view str) { return str; }
+
+asio::awaitable<std::string_view> echo_coro(std::string_view str) {
+  co_return str;
 }
 
-struct dummy{
+struct dummy {
   int add(int a, int b) { return a + b; }
 };
 int add(int a, int b) { return a + b; }
@@ -24,46 +26,50 @@ person get_person(person p) {
 void basict_usage() {
   rpc_server server("127.0.0.1:9004", 4);
   server.register_handler<echo>();
-  
+  server.register_handler<echo_coro>();
+
   dummy d{};
   server.register_handler<&dummy::add>(&d);
-  
+
   server.register_handler<get_person>();
-  
+
   auto ec = server.async_start();
-  if(ec) {
+  if (ec) {
     REST_LOG_ERROR << ec.message();
     return;
   }
-  
+
   auto rpc_call = []() -> asio::awaitable<void> {
     rpc_client client;
     auto ec0 = co_await client.connect("127.0.0.1:9004");
-    if(ec0) {
+    if (ec0) {
       REST_LOG_ERROR << ec0.message();
       co_return;
     }
-    
+
     auto r = co_await client.call<echo>("test");
-    if(r.ec==rpc_errc::ok) {
+    if (r.ec == rpc_errc::ok) {
       REST_LOG_INFO << "call result: " << r.value;
       assert(r.value == "test");
     }
-    
+
+    r = co_await client.call<echo_coro>("test1");
+    assert(r.value == "test1");
+
     auto r1 = co_await client.call<&dummy::add>(1, 2);
-    if(r1.ec==rpc_errc::ok) {
+    if (r1.ec == rpc_errc::ok) {
       REST_LOG_INFO << "call result: " << r1.value;
       assert(r1.value == 3);
     }
-    
+
     person p{1, "tom", 20};
     auto r2 = co_await client.call<get_person>(p);
-    if(r2.ec==rpc_errc::ok) {
+    if (r2.ec == rpc_errc::ok) {
       REST_LOG_INFO << "call result: " << r2.value.name;
       assert(r2.value.name == "jack");
     }
   };
-  
+
   sync_wait(get_global_executor(), rpc_call());
 }
 
@@ -72,26 +78,26 @@ void publish() {
   server.register_handler<echo>();
   server.register_handler<add>();
   server.async_start();
-  
+
   REST_LOG_INFO << "will pubish, waiting for input";
   auto pub = [&]() -> asio::awaitable<void> {
     std::string str;
     while (true) {
       std::cin >> str;
-      if(str == "quit") {
+      if (str == "quit") {
         break;
       }
-      
+
       co_await server.publish("topic1", str);
     }
   };
-  
+
   sync_wait(get_global_executor(), pub());
   server.stop();
 }
 
 int main() {
   basict_usage();
-  
+
   publish();
 }
\ No newline at end of file