Ferforms the first fetch. If it results in None, locks, performs the second fetch, and releases

FetchLockFetch.scala

package core

object FetchLockFetch {
	/**
		* Try to fetch using inexpensiveFetch, obtain lock, try again (using inexpensiveFetch),
		* fall back to more expensive expensiveFetch.
		*/
	def fetchLockFetch[T](inexpensiveFetch: => Option[T], lockFunc: => ((=> Option[T]) => Option[T]),
												expensiveFetch: => Option[T]): Option[T] =
		inexpensiveFetch.orElse{
			lockFunc(inexpensiveFetch.orElse(expensiveFetch))
		}
}