Discord.py Cog加载异常：hello命令未找到及成员欢迎失效问题

我使用Python开发Discord机器人，采用Cogs功能开发，严格遵循官方文档及视频教程操作，但Cog始终无法正常加载。执行hello命令时触发错误：

discord.ext.commands.bot: Ignoring exception in command None discord.ext.commands.errors.CommandNotFound: Command "hello" is not found

且新成员加入时无欢迎消息推送。

Cog代码 #

import discord
from discord.ext import commands, tasks


class Greetings(commands.Cog):
    def __init__(self, bot):
        self.bot = bot
        self._last_member = None

    @commands.Cog.listener()
    async def on_member_join(self, member):
        channel = member.guild.system_channel
        if channel is not None:
            await channel.send(f'Welcome {member.mention}.')

    @commands.command()
    async def hello(self, ctx, *, member: discord.Member = None):
        """Says hello"""
        member = member or ctx.author
        if self._last_member is None or self._last_member.id != member.id:
            await ctx.send(f'Hello {member.name}~')
        else:
            await ctx.send(f'Hello {member.name}... This feels familiar.')
        self._last_member = member

async def setup():
    await bot.add_cog(Greetings(bot))

main.py中的Cog加载函数 #

# Load cogs
async def load():
    for file in os.listdir('./cogs'):
        if file.endswith('.py'):
            await bot.load_extension(f'cogs.{file[:-3]}')

尝试的解决方法 #

• 重写hello命令
• 调整Cog加载逻辑

以上尝试均未解决问题。

最终解决方案 #

排查发现问题根源是缺少调用load()并启动机器人的主函数，添加后问题解决，主函数代码如下：

async def main():
    async with bot:
        await load()
        await bot.start(token)

内容的提问来源于stack exchange，提问作者paxanoA1607