implement Drop for client struct

src/lib.rs

@@ -618,7 +618,7 @@ fn derive_protocol(input: proc_macro2::TokenStream) -> proc_macro2::TokenStream
     // Create a struct which the client will use to communicate
     let client_recv_queue_wrapper = format_ident!("__{}RecvQueueWrapper", name);
     let client_struct = quote! {
-        #[derive(Clone)]
+        #[derive(::std::clone::Clone)]
         struct #client_recv_queue_wrapper {
             recv_queue: ::std::sync::Arc<::tokio::sync::Mutex<::tokio::sync::mpsc::Receiver<(u64, #answer_enum_name)>>>,
         }
@@ -707,6 +707,11 @@ fn derive_protocol(input: proc_macro2::TokenStream) -> proc_macro2::TokenStream
             }
             #(#client_impl)*
         }
+        impl std::drop::Drop for #client_struct_name {
+            fn drop(&mut self) {
+                self.close();
+            }
+        }
     };
 
     let expanded = quote! {