Workshop for Dedicated Servers
Dedicated servers can install addons straight from workshop collections, but it requires an addition to the startup parameter. The server will download the collection at startup.
First of all create a collection and find your collection ID. Do note that your collection needs to be public or unlisted, else, srcds won't be able to access it!
Append the following parameter to the server startup command-line:
An example could be:
The example below starts a dedicated server with 20 player slots. It downloads or updates all of the addons in collection 157384458. This collection includes the Zombie Survival gamemode and a few maps. It sets the gamemode to zombiesurvival and loads one of the downloaded maps.
Every time you restart your server it will check that these addons are all up to date.
View this short tutorial to see how it is set up.