The executor must be copied when an I/O object is move-assigned.

The moved-from I/O object needs to be left in the same state as if
constructed with a valid executor but without a resource.

asio/include/asio/detail/io_object_impl.hpp

@@ -96,8 +96,7 @@ public:
       service_->move_assign(implementation_,
           *other.service_, other.implementation_);
       executor_.~executor_type();
-      new (&executor_) executor_type(
-          std::move(other.executor_));
+      new (&executor_) executor_type(other.executor_);
       service_ = other.service_;
     }
     return *this;