From d57d060e5db54f781e73198f54ba709bae057678 Mon Sep 17 00:00:00 2001
From: Mark Burazin <mark@tahoma.hr>
Date: Fri, 10 Apr 2015 10:03:07 +0200
Subject: [PATCH] per http://tools.ietf.org/html/rfc6238 floor function needs
 to be used here.

---
 gototp.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gototp.go b/gototp.go
index 1d770c2..d07ea48 100644
--- a/gototp.go
+++ b/gototp.go
@@ -56,7 +56,7 @@ func (totp *TOTP) Now() int32 {
 // will be valid in the next period (FromNow(1)).
 // This means that every code is therefore valid for 3 * totp.Period.
 func (totp *TOTP) FromNow(periods int64) int32 {
-	period := (time.Now().Unix() / int64(totp.Period)) + int64(periods)
+	period := math.Floor(time.Now().Unix() / int64(totp.Period)) + int64(periods)
 	return totp.ForPeriod(period)
 }