sensu-plugins-aws ec2-node does not use credential keys

Trying to automate decommission in sensu of shutedterminated instances in AWS via ec2_node handler in sensu-aws plugin. i dont have AIM role assigned to instance and dont have credential file with AWS access for sensu user. i want to use json config to include keys. handler-ec2_node.rb file have a template of json config:

  {
    "aws": {
      "access_key": "adsafdafda",
      "secret_key": "qwuieohajladsafhj23nm",
      "region": "us-east-1c"
    }
  }

I created such file in conf.d directory setting appropriate credentials but get an error: 'require_credentials': unable to sign request without credentials set (Aws::Errors::MissingCredentialsError).

looks like sensu does not use my credentials. or this key:value must be with another key, not access_key and secret_key but something like secret_key_id and secret_key_id. i have tried different ways to solve this problem but did not succeed. any help will be appreciated.