code: func (f *FileLogger) Error(format string, v ...interface{}) {
  	_, file, line, _ := runtime.Caller(2) //calldepth=3
  	if f.logLevel <= ERROR {
  		f.logChan <- fmt.Sprintf("[%v:%v]", shortFileName(file), line) + fmt.Sprintf("\033[1;4;31m[ERROR] "+format+" \033[0m ", v...)
  	}
  }
docs: // error log