Consume int for new progress bar

[mih-kopylov]

When creating a new progress bar based on some collection length, it requires casting to int64.

bar := progressbar.Default(int64(len(sets.Repos)))

Not really nice, though I understand why it's int64 there.

Is there a change to consume int aside of int64?

[schollz]

yeah seems like a job for generics, now that they are available. Would accept a PR for this