curl --location --request POST 'https://slack.com/api/chat.scheduleMessage'{
    "channel": "C1H9RESGL",
    "message": {
        "attachments": [
            {
                "fallback": "This is an attachment's fallback",
                "id": 1,
                "text": "This is an attachment"
            }
        ],
        "bot_id": "B19LU7CSY",
        "subtype": "bot_message",
        "text": "Here's a message for you in the future",
        "type": "delayed_message",
        "username": "ecto1"
    },
    "ok": true,
    "post_at": "1562180400",
    "scheduled_message_id": "Q1298393284"
}