diff --git a/client/client.go b/client/client.go
index a99d730..e09b0a0 100644
--- a/client/client.go
+++ b/client/client.go
@@ -6,6 +6,7 @@ import (
 	"bufio"
 	"net"
 	"sync"
+	"time"
 )
 
 // One client connect to one server.
@@ -20,6 +21,8 @@ type Client struct {
 	conn                net.Conn
 	rw                  *bufio.ReadWriter
 
+	RespTimeout         time.Duration  // response timeout for do() in ms
+
 	ErrorHandler ErrorHandler
 }
 
@@ -31,6 +34,7 @@ func New(network, addr string) (client *Client, err error) {
 		respHandler:  make(map[string]ResponseHandler, queueSize),
 		innerHandler: make(map[string]ResponseHandler, queueSize),
 		in:           make(chan *Response, queueSize),
+		RespTimeout:  1000,
 	}
 	client.conn, err = net.Dial(client.net, client.addr)
 	if err != nil {
@@ -175,21 +179,26 @@ func (client *Client) handleInner(key string, resp *Response) *Response {
 	return resp
 }
 
+type handleOrError struct {
+	handle string
+	err error
+}
+
 func (client *Client) do(funcname string, data []byte,
 	flag uint32) (handle string, err error) {
 	if client.conn == nil {
 		return "", ErrLostConn
 	}
-	var mutex sync.Mutex
-	mutex.Lock()
+	var result = make(chan handleOrError, 1)
 	client.lastcall = "c"
 	client.innerHandler["c"] = func(resp *Response) {
-		defer mutex.Unlock()
 		if resp.DataType == dtError {
 			err = getError(resp.Data)
+			result <- handleOrError{"", err}
 			return
 		}
 		handle = resp.Handle
+		result <- handleOrError{handle, nil}
 	}
 	id := IdGen.Id()
 	req := getJob(id, []byte(funcname), data)
@@ -199,7 +208,15 @@ func (client *Client) do(funcname string, data []byte,
 		client.lastcall = ""
 		return
 	}
-	mutex.Lock()
+	var timer = time.After(client.RespTimeout * time.Millisecond)
+	select {
+	case ret := <-result:
+		return ret.handle, ret.err
+	case <-timer:
+		delete(client.innerHandler, "c")
+		client.lastcall = ""
+		return "", ErrLostConn
+	}
 	return
 }