Version not set in Docker container?

Hi, and 🙏 thank you for transfer.sh !

I am running it in Docker, and wanted to make a simple update notifier when new releases are tagged. So I wanted a way to return the current running version from a script.

Looking at the source, it seems that there is a `version` cli argument that should output the running version

https://github.com/dutchcoders/transfer.sh/blob/29d93c6da065f6fdf73654c682ae3cc656c70e6b/cmd/cmd.go#L317

but when I tried it, it's empty:

```
# docker pull dutchcoders/transfer.sh:latest
latest: Pulling from dutchcoders/transfer.sh
Digest: sha256:ebeded1b0ba4e23fb41b58c762b5e885559d625aa5ea48f70a9adc3170ed8c17
Status: Image is up to date for dutchcoders/transfer.sh:latest
docker.io/dutchcoders/transfer.sh:latest

# docker exec -it transfersh /go/bin/transfersh version
transfer.sh : Easy file sharing from the command line

```
Am I doing something wrong? Is there another way to retrieve the current version?