code: func NewAIA(cert *Certificate) *AIA {
  	if len(cert.cert.IssuingCertificateURL) == 0 {
  		return nil
  	}
  
  	// Arbitrary choice: store the first HTTP URL. We can always
  	// look up the other URLs later and replace this one if
  	// need be.
  	return &AIA{
  		SKI: cert.AKI,
  		URL: cert.cert.IssuingCertificateURL[0],
  	}
  }
docs: // NewAIA populates an AIA structure from a Certificate.