const runtime.traceEvGoWaiting

2 uses

	runtime (current package)
		trace.go#L54: 	traceEvGoWaiting         = 31 // denotes that goroutine is blocked when tracing starts [timestamp, goroutine id]
		trace.go#L236: 			traceEvent(traceEvGoWaiting, -1, uint64(gp.goid))