discovery/ec2/ec2.go
func (c *SDConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
	*c = DefaultSDConfig
	type plain SDConfig
	err := unmarshal((*plain)(c))
	if err != nil {
		return err
	}
	if c.Region == "" {
		sess, err := session.NewSession()
		if err != nil {
			return err
		}
		metadata := ec2metadata.New(sess)
		region, err := metadata.Region()
		if err != nil {
			return errors.New("EC2 SD configuration requires a region")
		}
		c.Region = region
	}
	for _, f := range c.Filters {
		if len(f.Values) == 0 {
			return errors.New("EC2 SD configuration filter values cannot be empty")
		}
	}
	return nil
}
func (c *SDConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
	*c = DefaultSDConfig
	type plain SDConfig
	err := unmarshal((*plain)(c))
	if err != nil {
		return err
	}
	if c.Region == "" {
		sess, err := session.NewSession()
		if err != nil {
			return err
		}
		metadata := ec2metadata.New(sess)
		region, err := metadata.Region()
		if err != nil {
			return errors.New("EC2 SD configuration requires a region")
		}
		c.Region = region
	}
	for _, f := range c.Filters {
		if len(f.Values) == 0 {
			return errors.New("EC2 SD configuration filter values cannot be empty")
		}
	}
	return nil
}
// UnmarshalYAML implements the yaml.Unmarshaler interface.