tasking/t.go
func (t *T) Fatalf(format string, args ...interface{}) {
	t.Errorf(format, args...)
	os.Exit(1)
}
func (t *T) Fatalf(format string, args ...interface{}) {
	t.Errorf(format, args...)
	os.Exit(1)
}
// Fatalf is equivalent to Errorf followed by a call to os.Exit(1).