Where to find the eventSub message id header?

API
4

The headers you listed in your OP are not from Twitch.

Since Twitch will send using a Go-http-client/1.1 based useragent and your headers show fetch

Example set of headers:

{
  host: 'REDACTED',
  'x-real-ip': 'REDACTED',
  'x-forwarded-for': 'REDACTED',
  'x-forwarded-proto': 'https',
  connection: 'close',
  'content-length': '557',
  'user-agent': 'Go-http-client/1.1',
  'content-type': 'application/json',
  'twitch-eventsub-message-id': 'b7ZqN7C4T8TBl3KWRLoA7C6bga3kf3-djGmleq6AnTw=',
  'twitch-eventsub-message-retry': '0',
  'twitch-eventsub-message-signature': 'sha256=REDACTED',
  'twitch-eventsub-message-timestamp': '2021-05-22T13:48:09.143057693Z',
  'twitch-eventsub-message-type': 'notification',
  'twitch-eventsub-subscription-is-batching-enabled': 'false',
  'twitch-eventsub-subscription-type': 'channel.follow',
  'twitch-eventsub-subscription-version': '1',
  'accept-encoding': 'gzip'
}

So that’s is a list of what you should get in your headers, when EventSub makes a call to you.

(x- headers are gonna vary by your server setup)