// NewCredentials returns a pointer to a new Credentials object wrapping the
// AssumeRoleProvider.  The credentials will expire every 15 minutes and the
// role will be named after a nanosecond timestamp of this operation.
//
// The sts and roleARN parameters are used for building the "AssumeRole" call.
// Pass nil as sts to use the default client.
//
// Window is the expiry window that will be subtracted from the expiry returned
// by the role credential request. This is done so that the credentials will
// expire sooner than their actual lifespan.
func NewCredentials(client AssumeRoler, roleARN string, window time.Duration) *credentials.Credentials {
	return credentials.NewCredentials(&AssumeRoleProvider{
		Client:       client,
		RoleARN:      roleARN,
		ExpiryWindow: window,
	})
}
// NewCredentials returns a pointer to a new Credentials object
// wrapping the EC2RoleProvider.
//
// Takes a custom http.Client which can be configured for custom handling of
// things such as timeout.
//
// Endpoint is the URL that the EC2RoleProvider will connect to when retrieving
// role and credentials.
//
// Window is the expiry window that will be subtracted from the expiry returned
// by the role credential request. This is done so that the credentials will
// expire sooner than their actual lifespan.
func NewCredentials(client *ec2metadata.Client, window time.Duration) *credentials.Credentials {
	return credentials.NewCredentials(&EC2RoleProvider{
		Client:       client,
		ExpiryWindow: window,
	})
}