Açıklaması şöyle
The Slack API base URL is https://slack.com/api and it uses token authentication. You can find your token in a Slack application that you need to create to start using the API. Token is visible in the configuration page of your application at https://api.slack.com/apps/YOUAR_APP_ID.
Yani "https://slack.com/api/chat.postMessage" adresine Token Authentication ile post yaparız
