I am using FCM API for send push notification on android and ios

I need to pass header parameters in post method.Is it possible?

I got below error:

Didn't run because: Unexpected HTTP response code: 401 (Unauthorized) Response body: The request was missing an Authentication Key (FCM Token). Please, refer to section "Authentication" of the FCM documentation, at https://firebase.google.com/docs/cloud-messaging/server.

The request was missing an Authentication Key (FCM Token). Please, refer to section "Authentication" of the FCM documentation, at https://firebase.google.com/docs/cloud-messaging/server.

Error 401

below is screen shot;