Swift implementation that uses Combine - Apple's Function Reactive Programming framework. As of 2022, this is an alternative approach to solving concurrency problems (in addition to async/await), especially if you are already using Combine.
Swift's HTTP/concurrency model seems to rely on file descriptors under the hood, in order for scenario 3 to succeed, the file descriptors limit must be increased:
ulimit -n 10000
Run the tests (manages scenario server in Docker):
swift test -c release
Run against a manually started scenario server:
swift run -c release