You are right, I misread this - UDM is something bundled with UCS installations, but there are several ways to query UDM from a remote machine:
- You could write a shell or Python script at the host and call it via RPC or SSH
- You could use Ansible: https://help.univention.com/t/best-practice-using-ansible-ucs-collections/19108
- But as you are already using Go the evident solution would be to use the UDM REST API
As the error is a Internal server error
you have to look at the UMC module log for the called UMC module, my guess is that the computer object has some attributes missing or misconfigured and therefore cannot be handled by the module.