code: func WithRequestCache(c context.Context) context.Context {
  	return context.WithValue(c, &requestCacheKey, lru.New(0))
  }
docs: // WithRequestCache initializes context-bound local cache and adds it to the
  // Context.
  //
  // The cache has unbounded size. This is fine, since the lifetime of the cache
  // is still scoped to a single request.
  //
  // It can be used as a second fast layer of caching in front of memcache.
  // It is never trimmed, only released at once upon the request completion.