const runtime.gcForceBlockMode

3 uses

	runtime (current package)
		mgc.go#L569: 	gcForceBlockMode               // stop-the-world GC now and STW sweep (forced by user)
		mgc.go#L683: 		mode = gcForceBlockMode
		mgc.go#L1695: 	if !concurrentSweep || mode == gcForceBlockMode {