diff --git a/client/client.go b/client/client.go
index 907704f..368363c 100644
--- a/client/client.go
+++ b/client/client.go
@@ -19,8 +19,8 @@ type Client struct {
 	sync.Mutex
 
 	net, addr, lastcall string
-	respHandler         map[string]ResponseHandler
-	innerHandler        map[string]ResponseHandler
+	respHandler         *responseHandlerMap
+	innerHandler        *responseHandlerMap
 	in                  chan *Response
 	conn                net.Conn
 	rw                  *bufio.ReadWriter
@@ -30,13 +30,40 @@ type Client struct {
 	ErrorHandler ErrorHandler
 }
 
+type responseHandlerMap struct {
+	sync.RWMutex
+	holder map[string]ResponseHandler
+}
+
+func newResponseHandlerMap() *responseHandlerMap {
+	return &responseHandlerMap{holder: make(map[string]ResponseHandler, queueSize)}
+}
+
+func (r *responseHandlerMap) remove(key string) {
+	r.Lock()
+	delete(r.holder, key)
+	r.Unlock()
+}
+
+func (r *responseHandlerMap) get(key string) (ResponseHandler, bool) {
+	r.RLock()
+	rh, b := r.holder[key]
+	r.RUnlock()
+	return rh, b
+}
+func (r *responseHandlerMap) put(key string, rh ResponseHandler) {
+	r.Lock()
+	r.holder[key] = rh
+	r.Unlock()
+}
+
 // Return a client.
 func New(network, addr string) (client *Client, err error) {
 	client = &Client{
 		net:             network,
 		addr:            addr,
-		respHandler:     make(map[string]ResponseHandler, queueSize),
-		innerHandler:    make(map[string]ResponseHandler, queueSize),
+		respHandler:     newResponseHandlerMap(),
+		innerHandler:    newResponseHandlerMap(),
 		in:              make(chan *Response, queueSize),
 		ResponseTimeout: DefaultTimeout,
 	}
@@ -155,7 +182,7 @@ func (client *Client) processLoop() {
 			resp = client.handleResponse(resp.Handle, resp)
 		case dtWorkComplete, dtWorkFail, dtWorkException:
 			client.handleResponse(resp.Handle, resp)
-			delete(client.respHandler, resp.Handle)
+			client.respHandler.remove(resp.Handle)
 		}
 	}
 }
@@ -167,7 +194,7 @@ func (client *Client) err(e error) {
 }
 
 func (client *Client) handleResponse(key string, resp *Response) *Response {
-	if h, ok := client.respHandler[key]; ok {
+	if h, ok := client.respHandler.get(key); ok {
 		h(resp)
 		return nil
 	}
@@ -175,9 +202,9 @@ func (client *Client) handleResponse(key string, resp *Response) *Response {
 }
 
 func (client *Client) handleInner(key string, resp *Response) *Response {
-	if h, ok := client.innerHandler[key]; ok {
+	if h, ok := client.innerHandler.get(key); ok {
 		h(resp)
-		delete(client.innerHandler, key)
+		client.innerHandler.remove(key)
 		return nil
 	}
 	return resp
@@ -195,7 +222,7 @@ func (client *Client) do(funcname string, data []byte,
 	}
 	var result = make(chan handleOrError, 1)
 	client.lastcall = "c"
-	client.innerHandler["c"] = func(resp *Response) {
+	client.innerHandler.put("c", func(resp *Response) {
 		if resp.DataType == dtError {
 			err = getError(resp.Data)
 			result <- handleOrError{"", err}
@@ -203,12 +230,12 @@ func (client *Client) do(funcname string, data []byte,
 		}
 		handle = resp.Handle
 		result <- handleOrError{handle, nil}
-	}
+	})
 	id := IdGen.Id()
 	req := getJob(id, []byte(funcname), data)
 	req.DataType = flag
 	if err = client.write(req); err != nil {
-		delete(client.innerHandler, "c")
+		client.innerHandler.remove("c")
 		client.lastcall = ""
 		return
 	}
@@ -217,7 +244,7 @@ func (client *Client) do(funcname string, data []byte,
 	case ret := <-result:
 		return ret.handle, ret.err
 	case <-timer:
-		delete(client.innerHandler, "c")
+		client.innerHandler.remove("c")
 		client.lastcall = ""
 		return "", ErrLostConn
 	}
@@ -239,7 +266,7 @@ func (client *Client) Do(funcname string, data []byte,
 	}
 	handle, err = client.do(funcname, data, datatype)
 	if err == nil && h != nil {
-		client.respHandler[handle] = h
+		client.respHandler.put(handle, h)
 	}
 	return
 }
@@ -272,14 +299,14 @@ func (client *Client) Status(handle string) (status *Status, err error) {
 	var mutex sync.Mutex
 	mutex.Lock()
 	client.lastcall = "s" + handle
-	client.innerHandler["s"+handle] = func(resp *Response) {
+	client.innerHandler.put("s"+handle, func(resp *Response) {
 		defer mutex.Unlock()
 		var err error
 		status, err = resp._status()
 		if err != nil {
 			client.err(err)
 		}
-	}
+	})
 	req := getRequest()
 	req.DataType = dtGetStatus
 	req.Data = []byte(handle)
@@ -295,10 +322,10 @@ func (client *Client) Echo(data []byte) (echo []byte, err error) {
 	}
 	var mutex sync.Mutex
 	mutex.Lock()
-	client.innerHandler["e"] = func(resp *Response) {
+	client.innerHandler.put("e", func(resp *Response) {
 		echo = resp.Data
 		mutex.Unlock()
-	}
+	})
 	req := getRequest()
 	req.DataType = dtEchoReq
 	req.Data = data