# File lib/aws/core/authorize_v4.rb, line 35
      def add_authorization! signer
        self.access_key_id = signer.access_key_id
        datetime = Time.now.utc.strftime("%Y%m%dT%H%M%SZ")
        headers['content-type'] ||= 'application/x-www-form-urlencoded'
        headers['host'] = host
        headers['x-amz-date'] = datetime
        headers['x-amz-security-token'] = signer.session_token if signer.session_token
        headers['authorization'] = authorization(signer, datetime)
      end