avoid reusing context object

fix https://github.com/chrislusf/seaweedfs/issues/1182

weed/server/volume_server_handlers_read.go

@@ -2,7 +2,7 @@ package weed_server
 
 import (
 	"bytes"
-	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -15,8 +15,6 @@ import (
 	"strings"
 	"time"
 
-	"encoding/json"
-
 	"github.com/chrislusf/seaweedfs/weed/glog"
 	"github.com/chrislusf/seaweedfs/weed/images"
 	"github.com/chrislusf/seaweedfs/weed/operation"
@@ -86,7 +84,7 @@ func (vs *VolumeServer) GetOrHeadHandler(w http.ResponseWriter, r *http.Request)
 	if hasVolume {
 		count, err = vs.store.ReadVolumeNeedle(volumeId, n)
 	} else if hasEcVolume {
-		count, err = vs.store.ReadEcShardNeedle(context.Background(), volumeId, n)
+		count, err = vs.store.ReadEcShardNeedle(volumeId, n)
 	}
 	// glog.V(4).Infoln("read bytes", count, "error", err)
 	if err != nil || count < 0 {