close

Closes this client, relinquishing any underlying resources.

This is purposefully not inherited from AutoCloseable because the client is long-lived and usually should not be synchronously closed via try-with-resources.

It's also usually not necessary to call this method at all. the default HTTP client automatically releases threads and connections if they remain idle, but if you are writing an application that needs to aggressively release unused resources, then you may call this method.