code: func RequestCache(c context.Context) *lru.Cache {
  	rc, _ := c.Value(&requestCacheKey).(*lru.Cache)
  	if rc == nil {
  		panic("server/caching: no request cache installed in Context")
  	}
  	return rc
  }
docs: // RequestCache retrieves a per-request in-memory cache of the Context. If no
  // request cache is installed, this will panic.