code: func (p *Pool) AddRefreshable(ctx context.Context, r Refreshable) {
  	id, err := p.lock.Lock()
  	if err == nil {
  		defer p.lock.Unlock(id)
  		p.refreshables = append(p.refreshables, r)
  		r.Refresh(ctx)
  	}
  }
docs: // Add a refreshable resource to the pool
  // Requires the RW lock and will not timeout like Refresh does