class Aws::AssumeRoleWebIdentityCredentials

def refresh
  # read from token file everytime it refreshes
  @assume_role_web_identity_params[:web_identity_token] = _token_from_file(@token_file)
  c = @client.assume_role_with_web_identity(
    @assume_role_web_identity_params).credentials
  @credentials = Credentials.new(
    c.access_key_id,
    c.secret_access_key,
    c.session_token
  )
  @expiration = c.expiration
end