(1...2).publisher.share() with `print`s and a `delay` to notice race condition.

debugging_shared_sequence_with_delay.swift

let upstream = (1...2)
	.publisher
	.print("\tPre-share")
	.share()
	.print("Post-share")

let cancellable = upstream
	.first()
	.delay(for: 1, scheduler: DispatchQueue.main) // ⇐
	.flatMap { first in
		upstream
			.prepend(first, first)
	}
	.pairwise()
	.sink(receiveValue: { _ in })

// Outputs (without the annotations):
// ```
// Post-share: receive subscription: (Multicast)
// Post-share: request unlimited
// 	Pre-share: receive subscription: (1...2)
// 	Pre-share: request unlimited
// 	Pre-share: receive value: (1)
// Post-share: receive value: (1)
// Post-share: receive cancel
// 	Pre-share: receive value: (2)
// 	Pre-share: receive finished
// Post-share: receive subscription: (Multicast)
// Post-share: request unlimited
// Post-share: receive finished ⇒ Downstream missed the `2` and instead only gets the completion replayed.
// ```