为什么列表追加在discord.py中不起作用？

import discord
from discord.ext import commands

intents = discord.Intents.default()
intents.messages = True

bot = commands.Bot(command_prefix='!', intents=intents)

# 定义一个全局列表
message_list = []

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

@bot.event
async def on_message(message):
    # 追加消息内容到全局列表
    message_list.append(message.content)
    await bot.process_commands(message)

# 启动事件循环
bot.run('YOUR_BOT_TOKEN')