Changed _pools initialization to an empty object

[clayzermk1]

What happens?

_pools is initialized as an empty array but values are stored and retrieved as object keys.

For example I have an object that looks like this in the inspector:

_pools: Array[0]
  "postgres://<snip>": Object
  length: 0

What did you expect to happen?

I'm not sure if this is by design or not. I was expecting an easily-iterable object of some sort, either an array of objects or a plain object with keys. Sure, I could iterate over the Array instance's own keys but that's messy. It feels like this should just have been instantiated as an object.

Use case

I understand this is a private variable. I use it to inspect the pool level for debugging and performance purposes only.

Thank you for your time and for such a great open source project! 🍻