discord.py cog

                                    import os
import discord
from discord.ext import commands

prefix = "?"
cogs_folder="./cogs"

bot = commands.Bot(command_prefix=prefix)

for file in cogs_folder:
  if file.endswith(".py"):
    try:
      bot.load_extension(f"cogs.{file[:-3]}")
      print(f"Loaded: {file}")
    except:
      print(f"Could not load: {file}")

                                    # bot file
import os
from discord.ext import commands

bot = commands.Bot(command_prefix='.')
# I am assuming that you have a test.py cog in a cogs folder
bot.load_extension('cogs.test') # this is good but you can make it better

for filename in os.listdir('./cogs'):
  if filename.endswith('.py'):
    bot.load_extension(f'cogs.{filename[:-3]}')
    
  else:
    print(f'Unable to load {filename[:-3]}')
    
bot.run(token)

                                    class Test(commands.cog):

    def __init__(self, client):
        self.client = client
        self._last_member = None

                                    from discord.ext import commands

class Ping(commands.Cog):
    """Receives ping commands"""
    
    @commands.command()
    async def ping(self, ctx: commands.Context):
        await ctx.send("Pong")

def setup(bot: commands.Bot):
    bot.add_cog(Ping())