RUSTSEC-2019-0031: spin is no longer actively maintained

[github-actions]

spin is no longer actively maintained

Details
Status	unmaintained
Package	spin
Version	0.5.2
URL	mvdnes/spin-rs@7516c80
Date	2019-11-21

The author of the spin crate does not have time or interest to maintain it.

Consider the following alternatives (both of which support no_std):

• conquer-once
• lock_api (a subproject of parking_lot)
  • spinning_top spinlock crate built on lock_api

See advisory page for additional details.