Deno logger FileHandler not writing to file

I'm trying to setup some loggers for an app. I have a console handler which write every log to the console. And a app handler which should write any log to some file.

The logs are writen correctly to the console, but none of the files are writen, and I can't get why.

import { setup as loggerSetup, getLogger } from "https://deno.land/std/log/mod.ts";
import {
  ConsoleHandler,
  FileHandler,
} from "https://deno.land/std/log/handlers.ts";
import { ensureDir } from "https://deno.land/std/fs/ensure_dir.ts";

const logDir = Deno.env.get("LOG_DIR") || "./logs";

await ensureDir(logDir);

const consoleLoggerHandler = new ConsoleHandler("DEBUG");
const applicationLoggerHandler = new FileHandler("DEBUG", {
  filename: logDir + "/application.log",
  formatter: "{msg}",
});
const errorLoggerHandler = new FileHandler("WARNING", {
  filename: logDir + "/errors.log",
});

await loggerSetup({
  handlers: {
    console: consoleLoggerHandler,
    app: applicationLoggerHandler,
    errors: errorLoggerHandler,
  },
  loggers: {
    default: {
      level: "DEBUG",
      handlers: ["console", "app"],
    },
    app: {
      level: "INFO",
      handlers: ["app"],
    },
    error: {
      level: "WARNING",
      handlers: ["errors"],
    },
  },
});

export const logger = getLogger();
export const appLogger = getLogger("app");
export const errorLogger = getLogger("error");

you have to call applicationLoggerHandler.flush() method in order to write on file.