code: func (c *ec2MetadataClientImpl) DefaultCredentials() (*RoleCredentials, error) {
  	securityCredential, err := c.client.GetMetadata(SecurityCrednetialsResource)
  	if err != nil {
  		return nil, err
  	}
  
  	securityCredentialList := strings.Split(strings.TrimSpace(securityCredential), "\n")
  	if len(securityCredentialList) == 0 {
  		return nil, errors.New("No security credentials in response")
  	}
  
  	defaultCredentialName := securityCredentialList[0]
  
  	defaultCredentialStr, err := c.client.GetMetadata(SecurityCrednetialsResource + defaultCredentialName)
  	if err != nil {
  		return nil, err
  	}
  	var credential RoleCredentials
  	err = json.Unmarshal([]byte(defaultCredentialStr), &credential)
  	if err != nil {
  		return nil, err
  	}
  	return &credential, nil
  }
docs: // DefaultCredentials returns the credentials associated with the instance iam role