code: func (h *SessionHandle) appendBindMeta(hash string, meta *BindMeta) {
  	// Make sure there is only one goroutine writes the cache.
  	h.ch.removeStaleBindMetas(hash, meta)
  	h.ch[hash] = append(h.ch[hash], meta)
  }
docs: // appendBindMeta addes the BindMeta to the cache, all the stale bindMetas are
  // removed from the cache after this operation.