const runtime.gcForceBlockMode

3 uses

	runtime (current package)
		mgc.go#L512: 	gcForceBlockMode               // stop-the-world GC now and STW sweep (forced by user)
		mgc.go#L622: 		mode = gcForceBlockMode
		mgc.go#L1471: 	if !_ConcurrentSweep || mode == gcForceBlockMode {