fix: duplex only has a getter

src/request.ts

@@ -13,7 +13,11 @@ export class Request extends GlobalRequest {
     }
     if (options?.body instanceof ReadableStream) {
       // node 18 fetch needs half duplex mode when request body is stream
-      ;(options as any).duplex = 'half'
+      Object.defineProperty(options, "duplex", {
+        get() {
+          return "half";
+        }
+      })
     }
     super(input, options)
   }