Added another test

app/notification_test.go

@@ -188,6 +188,15 @@ func TestGetExplicitMentions(t *testing.T) {
 				},
 			},
 		},
+		"AtUserWithPeriodAtEndOfSentence": {
+			Message:  "this is a message for @user.period.",
+			Keywords: map[string][]string{"@user.period": {id1}},
+			Expected: &ExplicitMentions{
+				MentionedUserIds: map[string]bool{
+					id1: true,
+				},
+			},
+		},
 		"UserWithPeriodAtEndOfSentence": {
 			Message:  "this is a message for user.period.",
 			Keywords: map[string][]string{"user.period": {id1}},