With a CS:GO server, you have the ability to add maps from the Steam Workshop directly to the server. And you can do this without having to upload the maps to the server. All you need to do is connect your server to the Workshop.
Note: The server must be in Advanced Mode for this to work!
To add a single map, add the following line to your autoexec.cfg:
host_workshop_map ID
Replace ID with the ID of the map. You can find the ID in the URL of the map.
For example, for the map aim_Courtyard: https://steamcommunity.com/sharedfiles/filedetails/?id=2648747794.
In this case, the ID would be 2648747794.
If you want to use multiple maps on the server, you need to create a collection on Steam. Then, add the desired maps to the collection.
Important: The collection and the maps included in it must be public! Otherwise, the server will not be able to download the collection with the maps.
Now, add the following line to your autoexec.cfg:
host_workshop_collection ID
Replace ID with the ID of the collection. You can find the ID in the URL of the collection.
For example, for the URL of a map: https://steamcommunity.com/sharedfiles/filedetails/?id=2648747794.
In this case, the ID would be 2648747794.
When you restart your server, the server will download the map or collection.