const runtime.traceEvGCBegin

2 uses

	runtime (current package)
		traceevent.go#L65: 	traceEvGCBegin            // GC start [timestamp, seq, stack ID]
		traceruntime.go#L323: 	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvGCBegin, traceArg(trace.seqGC), tl.stack(3))

The pages are generated with Golds v0.7.6. (GOOS=linux GOARCH=amd64)