diff --git a/client.c b/client.c
index 38bd807..7296c05 100644
--- a/client.c
+++ b/client.c
@@ -1,6 +1,5 @@
 #include "_nghttp2.h"
 
-#define ARRLEN(x) (sizeof(x) / sizeof(x[0]))
 
 // send_callback send data to network
 static ssize_t client_send_callback(nghttp2_session *session, const uint8_t *data,
@@ -113,7 +112,7 @@ static int on_client_frame_recv_callback(nghttp2_session *session,
         if (frame->headers.cat == NGHTTP2_HCAT_RESPONSE)
         {
             //fprintf(stderr, "All headers received\n");
-            OnClientFrameRecvCallback(user_data, frame->hd.stream_id);
+            OnClientHeadersDoneCallback(user_data, frame->hd.stream_id);
         }
         break;
     case NGHTTP2_RST_STREAM:
@@ -140,7 +139,7 @@ static int on_client_stream_close_callback(nghttp2_session *session, int32_t str
     return 0;
 }
 
-ssize_t data_source_read_callback(nghttp2_session *session, int32_t stream_id,
+static ssize_t data_source_read_callback(nghttp2_session *session, int32_t stream_id,
                                   uint8_t *buf, size_t length, uint32_t *data_flags,
                                   nghttp2_data_source *source, void *user_data)
 {
diff --git a/client.go b/client.go
index 06def36..b51aa13 100644
--- a/client.go
+++ b/client.go
@@ -6,6 +6,8 @@ package nghttp2
 */
 import "C"
 import (
+	"bytes"
+	"errors"
 	"fmt"
 	"io"
 	"log"
@@ -18,6 +20,10 @@ import (
 	"unsafe"
 )
 
+var (
+	errAgain = errors.New("again")
+)
+
 // ClientConn http2 connection
 type ClientConn struct {
 	session  *C.nghttp2_session
@@ -49,7 +55,13 @@ type dataProvider struct {
 	// drain the data
 	r io.Reader
 	// provider the data
-	w io.Writer
+	w        io.Writer
+	datach   chan []byte
+	errch    chan error
+	buf      *bytes.Buffer
+	run      bool
+	streamID int
+	session  *C.nghttp2_session
 }
 
 // NewClientConn create http2 client
@@ -238,6 +250,10 @@ func (c *ClientConn) CreateRequest(req *http.Request) (*http.Response, error) {
 		dp, cdp = newDataProvider(req.Body, nil)
 	}
 	streamID := C.submit_request(c.session, nva.nv, C.size_t(nvIndex), cdp)
+	if dp != nil {
+		dp.streamID = int(streamID)
+		dp.session = c.session
+	}
 	C.delete_nv_array(nva)
 	if int(streamID) < 0 {
 		return nil, fmt.Errorf("submit request error: %s",
@@ -282,10 +298,46 @@ func setNvArray(a *C.struct_nv_array, index int,
 		cvalue, cnamelen, cvaluelen, cflags)
 }
 
+func (dp *dataProvider) start() {
+	buf := make([]byte, 4096)
+	for {
+		n, err := dp.r.Read(buf)
+		if err != nil {
+			dp.errch <- err
+			break
+		}
+		dp.datach <- buf[:n]
+		C.nghttp2_session_resume_data(dp.session, C.int(dp.streamID))
+	}
+}
+
+// Read read from data provider
+// this emulate a unblocking reading
+// if data is not avaliable return errAgain
 func (dp *dataProvider) Read(buf []byte) (n int, err error) {
-	return dp.r.Read(buf)
+	if !dp.run {
+		go dp.start()
+		dp.run = true
+		time.Sleep(100 * time.Millisecond)
+	}
+
+	select {
+	case err := <-dp.errch:
+		//log.Println("d err ", err)
+		return 0, err
+	case b := <-dp.datach:
+		dp.buf.Write(b)
+	default:
+	}
+	n, err = dp.buf.Read(buf)
+	if err != nil {
+		//log.Println(err)
+		return 0, errAgain
+	}
+	return
 }
 
+// Write provider data for data provider
 func (dp *dataProvider) Write(buf []byte) (n int, err error) {
 	if dp.w == nil {
 		return 0, fmt.Errorf("write not supported")
@@ -295,7 +347,12 @@ func (dp *dataProvider) Write(buf []byte) (n int, err error) {
 
 func newDataProvider(r io.Reader, w io.Writer) (
 	*dataProvider, *C.nghttp2_data_provider) {
-	dp := &dataProvider{r, w}
+	dp := &dataProvider{
+		r: r, w: w,
+		errch:  make(chan error),
+		datach: make(chan []byte),
+		buf:    new(bytes.Buffer),
+	}
 	cdp := C.new_data_provider(C.size_t(uintptr(unsafe.Pointer(dp))))
 	return dp, cdp
 }
@@ -371,6 +428,10 @@ func DataSourceRead(ptr unsafe.Pointer,
 		if err == io.EOF {
 			return 0
 		}
+		if err == errAgain {
+			// NGHTTP2_ERR_DEFERED
+			return -508
+		}
 		return -1
 	}
 	cbuf := C.CBytes(gobuf)
@@ -446,9 +507,9 @@ func OnClientHeaderCallback(ptr unsafe.Pointer, streamID C.int,
 	return 0
 }
 
-// OnClientFrameRecvCallback callback function for begion to recv data
-//export OnClientFrameRecvCallback
-func OnClientFrameRecvCallback(ptr unsafe.Pointer, streamID C.int) C.int {
+// OnClientHeadersDoneCallback callback function for begion to recv data
+//export OnClientHeadersDoneCallback
+func OnClientHeadersDoneCallback(ptr unsafe.Pointer, streamID C.int) C.int {
 	//log.Println("frame recv")
 	conn := (*ClientConn)(ptr)
 	conn.onFrameRecv(int(streamID))