message: Fix get_bound_co.
diff: @@ -146,13 +146,19 @@ public:
  inline Coroutine* get_bound_co(const enum swEvent_type event)
  {
  if (likely(event & SW_EVENT_READ))
  + {
  + if (read_co)
  {
  return read_co;
  }
  + }
  if (event & SW_EVENT_WRITE)
  + {
  + if (write_co)
  {
  return write_co;
  }
  + }
  return nullptr;
  }
  