discord music bot

musicbot.py

import asyncio
import re
import json
import discord
from discord.ext import commands, tasks

from util import mp3_dl

BOT_TOKEN=""

bot = commands.Bot(command_prefix="!")

@bot.event
async def on_ready():
    print(f"Logged in as {bot.user}")

@bot.command()
async def play(ctx: commands.Context, arg):
    #check if arg is URL
    URL_PATTERN = "https?://[\w/:%#\$&\?\(\)~\.=\+\-]+"
    if not re.fullmatch(URL_PATTERN, arg):
        ctx.send("""This is not URL
        USAGE:
        \t!play {YouTube URL}""")
        return
    
    await ctx.send(f"Downloading {arg}")
    mp3_dl(arg)
    await ctx.send(f"Download finish")
    ctx.voice_client.play(discord.FFmpegPCMAudio("out.mp3"))
    

@bot.command()
async def join(ctx: commands.Context, *, arg):
    channel = ctx.author.voice.channel
    if channel is None:
        return await ctx.send("ボイスチャンネルに接続していません")

    await channel.connect()

bot.run(BOT_TOKEN)

util.py

import youtube_dl as ydl

def mp3_dl(url: str):
    ydl_opts = {
        'format': 'bestaudio/best',
        'postprocessors': [{
            'key': 'FFmpegExtractAudio',
            'preferredcodec': 'mp3',
            'preferredquality': '96',
        }],
        'outtmpl': 'out.%(ext)s',
        'noplaylist': True,
    }
    
    with ydl.YoutubeDL(ydl_opts) as dl:
        dl.download([url])