Upgrade ulid because of panics

[thpk]

I was testing out your modern go application, and left a container running for a few weeks (forgot to stop it). Tested again and I noticed some panics in the ulid generation.
It probably has to do with math.Rand not supporting concurrent use?

See issue in underlying package oklog/ulid#54

[sagikazarmark]

Thanks for reporting this issue, I'll take a look at it.