// Get
// function:
// - fetch stored value with the key
// - register lease
func (ss *Storageserver) Get(args *storageproto.GetArgs, reply *storageproto.GetReply) error {
	if !ss.isKeyInRange(args.Key) {
		reply.Status = storageproto.EWRONGSERVER
		return nil
	}

	req := &cacheReq{GET_VALUE, args.Key, ""}
	replyc := make(chan interface{})
	ss.cacheReqC <- Request{req, replyc}
	value := <-replyc
	if value != nil {
		lsplog.Vlogf(5, "Return Value %s", args.Key)
		reply.Status = storageproto.OK
		reply.Value = value.(string)
		// lease
		if args.WantLease {
			req := &cacheReq{PUT_LEASE, args.Key, args.LeaseClient}
			replyc := make(chan interface{})
			ss.cacheReqC <- Request{req, replyc}
			status := (<-replyc).(bool)
			if status {
				lsplog.Vlogf(5, "Get Lease successfully %s", args.Key)
				reply.Lease.Granted = true
				reply.Lease.ValidSeconds = storageproto.LEASE_SECONDS
			} else {
				lsplog.Vlogf(5, "Get Lease failed %s", args.Key)
				reply.Lease.Granted = false
			}
		} else {
			reply.Lease.Granted = false
		}
	} else {
		lsplog.Vlogf(5, "Value not found %s", args.Key)
		reply.Status = storageproto.EKEYNOTFOUND
	}
	return nil
}