priorityq - generic priority queue in Go

This module was inspired by a reddit post wherein /u/zandery23 asked how to implement a priority queue in Go. A fantastic solution was provided by /u/Ploobers. That's probably right for 99 out of 100 use cases, but it's not completely precise.

Particularly, the second select block does not guarantee that an item from the priority queue will be taken if there is also an item in the regular queue.

select {
case job := <-mq.priorityQueue:
    // ...
case job := <-mq.regularQueue:
    // ...
// ...
}

From the Go Language Specification:

If one or more of the communications can proceed, a single one that can proceed is chosen via a uniform pseudo-random selection.

Thus, it is possible for the second case to be chosen even if the first case is also ready.

The precise package in this module implements a concurrent priority queue that guarantees receipt of a high-priority items before low-priority ones. This is primarily a fun exercise, I cannot recommend that anyone actually use this in a real project.