I was really bored so I made a file sharing service which uses AES GCM. It was actually very challenging to get working as this was the first project I have personally worked on where being careful with memory usage was extremely important (Go's AES GCM implementation requires a buffer to be in memory to encrypt/decrypt).
(link is dead and no longer being hosted :()
Files get deleted after one hour by a cron job, if you want to play with it. Currently I've implemented the local file system as the only mechanism of storage, but I plan to add Amazon S3 support soon (I will be making use of DigitalOcean spaces).
I plan to turn Dump Me into a larger project but I ended up just making this basic demo because why not. I learned from it that this isn't end to end encryption, and if I want that I'll have to encrypt on the client. Encrypting/decrypting on the server has several obvious attack vectors (RAM leaking, stealing temporary files), but it's better than always having all unencrypted data.
Web UI (I don't know why you would care): https://github.com/therealpaulgg/dumpme-ui