Description

This PR fixes a crash occurring on iOS/macOS when NWPathMonitor updates are processed concurrently while the monitor is being deallocated.

The crash manifests as swift::fatalError / swift_deallocPartialClassInstance / double free.

The NWPathMonitor was previously initialized on a global concurrent queue (DispatchQueue.global(qos: .utility)). This allowed race conditions where the pathUpdateHandler block could still be executing on one thread while stop() was setting pathMonitor = nil on another, leading to memory corruption.

Fix: Changed the queue to a private serial DispatchQueue. This ensures that start, stop, and update events are processed sequentially, preventing the race condition.

Related Issues

• Fix [Bug] connectivity_plus iOS Crash: swift::fatalError in NWPathMonitor (race condition) #3753

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I titled the PR using Conventional Commits.
• I did not modify the CHANGELOG.md nor the plugin version in pubspec.yaml files.
• All existing and new tests are passing.
• The analyzer (flutter analyze) does not report any problems on my PR.

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change (please indicate that with a ! in the title as explained in Conventional Commits).
• No, this is not a breaking change.