From b2940955ab8b26e19d43a43c4da0475dd81bdb56 Mon Sep 17 00:00:00 2001
From: miraclesu <suchuangji@gmail.com>
Date: Mon, 25 Jan 2016 14:19:23 +0800
Subject: [PATCH] fix reader nil pointer

---
 tail.go | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/tail.go b/tail.go
index 307a026..6f77661 100644
--- a/tail.go
+++ b/tail.go
@@ -143,11 +143,17 @@ func (tail *Tail) Tell() (offset int64, err error) {
 		return
 	}
 	offset, err = tail.file.Seek(0, os.SEEK_CUR)
-	if err == nil {
-		tail.lk.Lock()
-		offset -= int64(tail.reader.Buffered())
-		tail.lk.Unlock()
+	if err != nil {
+		return
 	}
+
+	tail.lk.Lock()
+	defer tail.lk.Unlock()
+	if tail.reader == nil {
+		return
+	}
+
+	offset -= int64(tail.reader.Buffered())
 	return
 }