'Transaction' is only available in iOS 13.0 or newer

[chocoford]

In File Transaction.swift.

The extension of Transaction only marked as @available(macOS 10.15, *)

@available(macOS 10.15, *) // <-- here
extension Transaction: NIOAsyncSequenceProducerDelegate {
    @usableFromInline
    func produceMore() {
...

[dnadoba]

Good catch! Do you want me to take care of this or do you want to open a small PR to fix this?