Sending a Slack message with fetch

I like using Slack bots for things like alerts and notifications and have needed this snippet enough to leave it here.

I use slack-block-builder to build the message; writing raw slack blocks is a pain.

const res = await fetch('https://slack.com/api/chat.postMessage', {
  method: 'POST',
  headers: {
    // IMPORTANT! You need to set the charset to utf-8
    'Content-Type': 'application/json; charset=utf-8',
    // Create an app: https://api.slack.com/apps
    Authorization: `Bearer ${process.env.SLACK_BOT_TOKEN}`,
  },
  body: Message()
    // Get this from Slack or the channel URL.
    // Be sure to invite the bot to the channel.
    .channel('C1234567890')
    .blocks(Blocks.Section().text('*Error:* ' + error), Blocks.Divider())
    .buildToJSON(),
})