code: func (c certificate) String() string {
  	b, err := asn1.Marshal(c)
  	if err != nil {
  		return fmt.Sprintf("Failed marshaling cert: %v", err)
  	}
  	block := &pem.Block{
  		Bytes: b,
  		Type:  "CERTIFICATE",
  	}
  	b = pem.EncodeToMemory(block)
  	return string(b)
  }
docs: // String returns a PEM representation of a certificate