Reader.Close: Prefer to lock Client in public method

reader.go

@@ -208,6 +208,8 @@ func (r *Reader) readOnceAt(b []byte, pos int64, ctxErr *error) (n int, err erro
 }
 
 func (r *Reader) Close() error {
+	r.t.cl.mu.Lock()
+	defer r.t.cl.mu.Unlock()
 	r.t.deleteReader(r)
 	r.t = nil
 	return nil

t.go

@@ -136,8 +136,6 @@ func (t *Torrent) addReader(r *Reader) {
 }
 
 func (t *Torrent) deleteReader(r *Reader) {
-	t.cl.mu.Lock()
-	defer t.cl.mu.Unlock()
 	delete(t.readers, r)
 	t.readersChanged()
 }