check expired session.

chatSession.go

 				log.Printf("Session Content [path=%s] not correct: ", path)
 				result = createEmptySession(openID, 3600)
 			} else { //load procedure state if any
-				procedure := result.Procedure
-				result.state, err = getCurrentState(openID, procedure)
+				if !isExpired(result.Expire) {
+					procedure := result.Procedure
+					result.state, err = getCurrentState(openID, procedure)
+				} else {
+					result = createEmptySession(openID, 3600)
+				}
 			}
 		}
 	}