[beekld]

Summary

#489 made FDv2.Stop() broadcast an Off status after its goroutines exit. A broadcast does a blocking send to each listener channel, which buffers 10 values. If an application listener stops reading while its buffer is full, Stop() blocks forever. That hangs LDClient.Close(), and GetStatus() hangs with it, because the send ran under the status lock.

The hazard predates #489. Any status update can block the same way while the data system runs, and the broadcaster holds its lock during the send. So removing the stuck listener also blocks.

This PR:

• Makes RemoveListener and Close unblock a send to a full listener. Listeners that keep reading still get every value, in order. No broadcast drops events.
• Sends the FDv2 data source status broadcast after the status lock is released, as FDv1 already does. GetStatus() no longer waits on a listener.
• Stops broadcasting Off from FDv2.Stop(). The status still changes to Off, and listeners learn of shutdown when their channels close.
• Removes the drain goroutines in the FDv1 and FDv2 WaitFor that only existed to work around the blocking removal.
• Makes WaitFor return false when its listener channel closes, in both FDv1 and FDv2. Before, a WaitFor still running at Close() spun on the closed channel until its timeout.

---

Note

Overview
Fixes hangs when a status listener’s buffered channel is full and the app stops reading—previously Broadcast, RemoveListener, Close, FDv2.Stop(), and GetStatus() could block indefinitely (including LDClient.Close()).

The generic Broadcaster now sends without holding the subscriber list lock, uses per-subscriber done signaling so removal/shutdown aborts in-flight sends, and still delivers every value in order to listeners that keep reading. FDv2.UpdateStatus broadcasts only after the status mutex is released (matching FDv1). Stop() sets status to Off internally but no longer broadcasts Off—shutdown is signaled by closing listener channels. WaitFor drops the old channel-drain workaround and returns false when the listener channel closes (e.g. on stop or broadcaster close).

Tests cover full-buffer broadcast/unblock paths and FDv1/FDv2 WaitFor, GetStatus, and Stop under a full listener.

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[kinyoklion]

Approved with consideration of 505.

[tanderson-ld]

Requires 505 for stack to merge together.