code: func (c *RegionCache) GetStoreAddr(bo *Backoffer, id uint64) (string, error) {
  	c.storeMu.RLock()
  	if store, ok := c.storeMu.stores[id]; ok {
  		c.storeMu.RUnlock()
  		return store.Addr, nil
  	}
  	c.storeMu.RUnlock()
  	return c.ReloadStoreAddr(bo, id)
  }
docs: // GetStoreAddr returns a tikv server's address by its storeID. It checks cache
  // first, sends request to pd server when necessary.