This crate provides a Pool struct that allows taking Leasees and using them.
When a Lease is dropped it is automatically returned to the pool.
One nice thing about this api is that the lifetime of a Lease is not connected to the lifetime
of a Pool so they can be sent across threads.
async
Pool::get_async() function. Async brings a little bit of overhead to getting
leases so it is behind a feature.stream
async feature and adds the Pool::stream() function for creating a stream
of leases that resolve anytime there is an available Lease