SafeOnly fetch data iff it has been cached. Useful for example when a database connection is being cached, and it has to be closed when it is no longer needed, but should not be opened just to be closed.Fetch data from a cacheVCreate a cache which will execute an (IO ()) function on demand a maximum of 1 times.7Create a cache with a timeout from an (IO ()) function.  Cache!, the cache to fetch a value fromFetcher>, the function that returns the data which should be cached. TimeoutP in microseconds before the cache is erased, 0 to disable emptying of the cacheresetTimerOnRead, if true the timeout will be reset every time the cache is read, otherwise it will only be reset when the cached value is set.FetcherA, the function that returns the data which should be cached. If TimeoutP is not set to zero, this function must be allowed to be called more than once.     /Concurrent-Cache-0.2.1.0-1WOMn4Z0brZCpz1J1PV0bwControl.Concurrent.Cache CachedData fetchCachedfetchcreateReadOnceCachecreateTimedCacheTimedCachedDataReadOnceCachedDataTimeoutTimeSinceCreationTimeSinceLastRead