fix the session memcache bug

@@ -129,8 +129,9 @@ func (rp *MemProvider) SessionRead(sid string) (session.SessionStore, error) {
 		}
 	}
 	item, err := client.Get(sid)
-	if err != nil {
-		return nil, err
+	if err != nil && err == memcache.ErrCacheMiss {
+		rs := &MemcacheSessionStore{sid: sid, values: make(map[interface{}]interface{}), maxlifetime: rp.maxlifetime}
+		return rs, nil
 	}
 	var kv map[interface{}]interface{}
 	if len(item.Value) == 0 {
@@ -141,7 +142,6 @@ func (rp *MemProvider) SessionRead(sid string) (session.SessionStore, error) {
 			return nil, err
 		}
 	}
-
 	rs := &MemcacheSessionStore{sid: sid, values: kv, maxlifetime: rp.maxlifetime}
 	return rs, nil
 }

@@ -143,12 +143,14 @@ func (manager *Manager) SessionStart(w http.ResponseWriter, r *http.Request) (se
 			return nil, errs
 		}
 		session, err = manager.provider.SessionRead(sid)
-		cookie = &http.Cookie{Name: manager.config.CookieName,
+		cookie = &http.Cookie{
+			Name:     manager.config.CookieName,
 			Value:    url.QueryEscape(sid),
 			Path:     "/",
 			HttpOnly: true,
 			Secure:   manager.isSecure(r),
-			Domain:   manager.config.Domain}
+			Domain:   manager.config.Domain,
+		}
 		if manager.config.CookieLifeTime > 0 {
 			cookie.MaxAge = manager.config.CookieLifeTime
 			cookie.Expires = time.Now().Add(time.Duration(manager.config.CookieLifeTime) * time.Second)
@@ -170,12 +172,14 @@ func (manager *Manager) SessionStart(w http.ResponseWriter, r *http.Request) (se
 				return nil, err
 			}
 			session, err = manager.provider.SessionRead(sid)
-			cookie = &http.Cookie{Name: manager.config.CookieName,
+			cookie = &http.Cookie{
+				Name:     manager.config.CookieName,
 				Value:    url.QueryEscape(sid),
 				Path:     "/",
 				HttpOnly: true,
 				Secure:   manager.isSecure(r),
-				Domain:   manager.config.Domain}
+				Domain:   manager.config.Domain,
+			}
 			if manager.config.CookieLifeTime > 0 {
 				cookie.MaxAge = manager.config.CookieLifeTime
 				cookie.Expires = time.Now().Add(time.Duration(manager.config.CookieLifeTime) * time.Second)