Sometimes, cannot quit gracefully

[thinkAfCod]

Expected behaviour

When to kill, shisui could be quit with 100% certainty.

Actual behaviour

Sometimes, shisui cannot quit gracefully. And it may be blocked after printing the log:

if len(clientChan) == 0 {
	log.Warn("Waiting for the client to start...")
}
c := <-clientChan
c.closePortalRpcServer()