Use `request.post` instead of `get`, makes it possible to send a lot bigger messages (Slack API returned HTTP errors because of too long query string when using get).
Use `request.post` instead of `get`, makes it possible to send a lot bigger messages (Slack API returned HTTP errors because of too long query string when using get).

oscar-b/slack-bot-api,mishk0/slack-bot-api,greenlikeorange/slack-bot-api