La discordia bot no vaya en línea

Agregar await client.process_commands(ctx) y @client.event no necesita paréntesis(). Utilice el código siguiente:

@client.event
async def on_message(ctx):
  if ctx.author == client.user:
    return

  await client.process_commands(ctx)

Utilice este código completo si aún así no funciona:

import discord
from discord.ext import commands

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


@bot.event
async def on_ready():
  print('We are logged in!')

@bot.event
async def on_message(message):
   if message.author==bot.user: 
     return

   await bot.process_commands(message)

@bot.command()
async def ping(message) :
   await message.channel.send("Pong!!")

bot.run("TOKEN")

Usted debe intentar este lugar

import os
import discord
from discord.ext import commands

discord_token = "Your Token"

client = discord.Client()

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

@client.command()
async def on_ready():
  print("running")

other codes here...

bot.run(discord_token)

El código que usted le dio es incorrecto, esto es correcto:

import os 
import discord
from discord.ext import commands

bot = commands.Bot(command_prefix="!") # you don't need an extra discord.client Bot is enough
token = os.getenv("TOKEN")
#you should not run the program here you should run it at last

@bot.event #no need for brackets
async def on_ready():
  print("running")

@bot.event
async def on_message(ctx):
  if ctx.author == client.user:
    return

@bot.command(name="span",description="YOUR DESCRIPTION HERE") # it is command and not commands
async def span_(ctx,amount:int,*,message):
  for i in range(amount):
    await ctx.send(message)

bot.run(token) #you should run the bot now only and this will work perfectly!

Usted puede encontrar la documentación para discord.py aquí.