code: func onShow(cf *CLIConf) {
  	key, _, err := loadIdentity(cf.IdentityFileIn)
  
  	// unmarshal certificate bytes into a ssh.PublicKey
  	cert, _, _, _, err := ssh.ParseAuthorizedKey(key.Cert)
  	if err != nil {
  		utils.FatalError(err)
  	}
  
  	// unmarshal private key bytes into a *rsa.PrivateKey
  	priv, err := ssh.ParseRawPrivateKey(key.Priv)
  	if err != nil {
  		utils.FatalError(err)
  	}
  
  	pub, err := ssh.ParsePublicKey(key.Pub)
  	if err != nil {
  		utils.FatalError(err)
  	}
  
  	fmt.Printf("Cert: %#v\nPriv: %#v\nPub: %#v\n",
  		cert, priv, pub)
  
  	fmt.Printf("Fingerprint: %s\n", ssh.FingerprintSHA256(pub))
  }
docs: // onShow reads an identity file (a public SSH key or a cert) and dumps it to stdout