Use a shared string for example HTTP server doc roots

fix #1109

example/http/server/coro/http_server_coro.cpp

@@ -251,7 +251,7 @@ struct send_lambda
 void
 do_session(
     tcp::socket& socket,
-    std::string const& doc_root,
+    std::shared_ptr<std::string const> const& doc_root,
     boost::asio::yield_context yield)
 {
     bool close = false;
@@ -274,7 +274,7 @@ do_session(
             return fail(ec, "read");
 
         // Send the response
-        handle_request(doc_root, std::move(req), lambda);
+        handle_request(*doc_root, std::move(req), lambda);
         if(ec)
             return fail(ec, "write");
         if(close)
@@ -298,7 +298,7 @@ void
 do_listen(
     boost::asio::io_context& ioc,
     tcp::endpoint endpoint,
-    std::string const& doc_root,
+    std::shared_ptr<std::string const> const& doc_root,
     boost::asio::yield_context yield)
 {
     boost::system::error_code ec;
@@ -354,7 +354,7 @@ int main(int argc, char* argv[])
     }
     auto const address = boost::asio::ip::make_address(argv[1]);
     auto const port = static_cast<unsigned short>(std::atoi(argv[2]));
-    std::string const doc_root = argv[3];
+    auto const doc_root = std::make_shared<std::string>(argv[3]);
     auto const threads = std::max<int>(1, std::atoi(argv[4]));
 
     // The io_context is required for all I/O