I think I've found the issue.

It's because the files don't exist in the destination configured here: 
https://github.com/bitvora/wot-relay/blob/master/docker-compose.yml#L11
And these paths are defined in the .env:
https://github.com/bitvora/wot-relay/blob/master/.env.example#L13
which are loaded / used in the Go binary.

So what is described that you only should edit the left side before the colon is incorrect? So '- "./templates/index.html:/app/templates/index.html"' should be the same as the INDEX_PATH value in the .env. The same logic applies for the STATIC_PATH.