runtime/trace: TestSubscribers/start(flight)_start(trace)_stop(flight)_stop(trace) failures

[gopherbot]

#!watchflakes
default <- pkg == "runtime/trace" && test == "TestSubscribers/start(flight)_start(trace)_stop(flight)_stop(trace)"

Issue created automatically to collect these failures.

Example (log):

=== RUN   TestSubscribers/start(flight)_start(trace)_stop(flight)_stop(trace)
    subscribe_test.go:41: unexpected error reading trace for tracer: expected a goroutine but didn't have one
--- FAIL: TestSubscribers/start(flight)_start(trace)_stop(flight)_stop(trace) (0.05s)

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "runtime/trace" && test == "TestSubscribers/start(flight)_start(trace)_stop(flight)_stop(trace)"

2025-12-08 15:59 gotip-windows-386 go@4122d3e9 runtime/trace.TestSubscribers/start(flight)_start(trace)_stop(flight)_stop(trace) (log)

=== RUN   TestSubscribers/start(flight)_start(trace)_stop(flight)_stop(trace)
    subscribe_test.go:41: unexpected error reading trace for tracer: expected a goroutine but didn't have one
--- FAIL: TestSubscribers/start(flight)_start(trace)_stop(flight)_stop(trace) (0.05s)

— watchflakes