下次请阅读不一致的API文档

api = "https://canary.discord.com/api/v8"
message = ""
guilds = requests.get(
    f"{api}/users/@me/guilds",
    headers=headers
).json()

for guild in guilds:
    channels = requests.get(
        f"{api}/guilds/{guild['id']}/channels",
        headers = headers
    ).json()
    for channel in channels:
        time.sleep(1) #ratelimit moment
        r = requests.post(
            f"{api}/channels/{channel['id']}/messages",
            headers=headers,
            data={"content": message}
        )
        print(f"sent message to {channel['id']} {r}")