code: func NewSMTPClient(apiKeyPublic, apiKeyPrivate string) *SMTPClient {
  	auth := smtp.PlainAuth(
  		"",
  		apiKeyPublic,
  		apiKeyPrivate,
  		HostSMTP,
  	)
  	return &SMTPClient{
  		host: fmt.Sprintf("%s:%d", HostSMTP, PortSMTP),
  		auth: auth,
  	}
  }
docs: // NewSMTPClient returns a new smtp client wrapper