[feature request] naming workerpools

[thediveo]

First, so many thanks for your workerpool module that is exactly what I've been looking for!

In my projects I tend to use several worker pools and I use them for transient work only, so these are not worker pools kept around all the time a service is up. Instead, I create worker pools as needed for individual requests (and there are some reasons for not sharing certain workers across different service requests).

When unit testing my service handlers for goroutine leaks (using Gomega's at this time still brand new gleak goroutine leak tester) I noticed that it would be quite nice for diagnosing if workerpools and their workers could be individually identified by some name. The name of a worker could simply be the one of its pool for simplicity. Would you be interested in a PR?