Get the full list of my own YouTube channel's subscriber

I am trying to get the full list of my own channel's subscribers, but this does not work.

https://www.googleapis.com/youtube/v3/subscriptions?part=snippet&mine=true&key=[API_KEY]

I am following the official documentation https://developers.google.com/youtube/v3/docs/subscriptions/list

But get this error

{"error": {"code": 401,"message": "The request uses the \u003ccode\u003emine\u003c/code\u003e parameter but is not properly authorized.","errors": [      {"message": "The request uses the \u003ccode\u003emine\u003c/code\u003e parameter but is not properly authorized.","domain": "youtube.parameter","reason": "authorizationRequired","location": "mine","locationType": "parameter"      }    ]  }}