code: func (c *CertChecker) CheckHostKey(addr string, remote net.Addr, key ssh.PublicKey) error {
  	err := validate(key)
  	if err != nil {
  		return trace.Wrap(err)
  	}
  
  	return c.CertChecker.CheckHostKey(addr, remote, key)
  }
docs: // CheckHostKey checks the validity of a host certificate.