Laravel Passport client_credentials

Good Day does any one using the method like this one ? https://laravel.com/docs/5.4/passport#client-credentials-grant-tokens

i try to make registration API that has client_id and client_secret only and i want the return that as access token, refresh token, expire_date but the return of the www.url.com/oauth/token is this

{
 "error": "unsupported_grant_type",
 "message": "The authorization grant type is not supported by the authorization server.",
 "hint": "Check the `grant_type` parameter"
}

anyone can help me.. ? thanks in advance

via AiX En