I'm pretty interested in this feature as well but rspotify doesn't seem to have any options to add a song to a queue. I can't seem to find anything on the Spotify Web API Reference either.

Yea you're right, everyone is still waiting on Spotify to add the API endpoint:
spotify/web-api#462

I'd love this feature too

Doesn't look like spotify gives a damn about this. Alternatively a local queue could be added.

Something like "OnSongEnd: if queue.size > 0; play(queue.pop)". The queue could be completly unrelated to playing playlists, albums or radios, just the like the official queue. I think this would be a great compromise.

https://developer.spotify.com/console/post-queue/
https://developer.spotify.com/documentation/web-api/reference/player/add-to-queue/

This endpoint isn't working for me either. Probably not ready yet then. Really irks me because its easily one of the most used UI actions. @Bios-Marcel that seems like a good solution.

EDIT:
I lied it is indeed working. It just never returned a response to the web client they have there. I'm sitting here jamming to:
spotify:track:4nC3lnqFUrkwuImM8WTrap

And I thought to myself, dang this song is a lot longer than I remembered... Queued up like 10 times from me mashing the API call. Well At least they have the functionality there albeit not quite ready.

Thanks @WMcKibbin! Looks like this is a new endpoint not yet covered by rspotify, I will look into adding it there so we can start supporting queues!

Any updates on the queuing feature?

Looks like rspotify has added this endpoint as of yesterday 🎉 https://github.com/ramsayleung/rspotify/commits/master

Once rspotify has released we can start working on it 👍

it seems implemented in rspotify now. I really wanted to try implementing it but...
I neved did rust before :'(
any update for this tho?

Thanks to @BeneCollyridam this is now possible!

Awesome, good work everybody!