code: func (i *Identity) SSHClientConfig() *ssh.ClientConfig {
  	return &ssh.ClientConfig{
  		User: i.ID.HostUUID,
  		Auth: []ssh.AuthMethod{
  			ssh.PublicKeys(i.KeySigner),
  		},
  		HostKeyCallback: i.hostKeyCallback,
  		Timeout:         defaults.DefaultDialTimeout,
  	}
  }
docs: // SSHClientConfig returns a ssh.ClientConfig used by nodes to connect to
  // the reverse tunnel server.