timeout的bug

[eruca]

// 设置超时
		deadline := time.Now().Add(time.Nanosecond * time.Duration(NumNanosecondsInAMillisecond*request.Timeout))
		for shard := 0; shard < engine.initOptions.NumShards; shard++ {
			select {
			case rankerOutput := <-rankerReturnChannel:
				if !request.CountDocsOnly {
					for _, doc := range rankerOutput.docs {
						rankOutput = append(rankOutput, doc)
					}
				}
				numDocs += rankerOutput.numDocs
			case <-time.After(deadline.Sub(time.Now())):
				isTimeout = true
				break
			}
		}

如果设置了超时，而且确实是超时了，那么进入 下面那条case了，那么原来的rankerReturnChannel要返回的rankerOut就无法正常返回了，阻塞了，而且会影响下次search的结果会返回上次是结果