diff --git a/ioutil/cancel_reader.go b/ioutil/cancel_reader.go
index 4c1b661..4825b70 100644
--- a/ioutil/cancel_reader.go
+++ b/ioutil/cancel_reader.go
@@ -21,19 +21,25 @@ type CancelableReader struct {
 
 func (c *CancelableReader) begin() {
 	for {
-		sizewant := <-c.sizeWant
-		buf := make([]byte, sizewant)
-		// readFull, cause some readers like net.TCPConn returns size smaller than buf size
-		n, err := io.ReadFull(c.r, buf)
-		if err != nil {
-			c.err = err
+		select {
+		case sizeWant := <-c.sizeWant:
+			buf := make([]byte, sizeWant)
+			// readFull, cause some readers like net.TCPConn returns size smaller than buf size
+			n, err := io.ReadFull(c.r, buf)
+			if err != nil {
+				c.err = err
+				close(c.data)
+				return
+			}
+			if n != sizeWant {
+				panic("read " + strconv.Itoa(n) + ", want " + strconv.Itoa(sizeWant))
+			}
+			c.data <- buf
+		case <-c.ctx.Done():
 			close(c.data)
+			close(c.sizeWant)
 			return
 		}
-		if n != sizewant {
-			panic("read " + strconv.Itoa(n) + ", want " + strconv.Itoa(sizewant))
-		}
-		c.data <- buf
 	}
 }