[bug] fix CI error

[hsluoyz]

Need to fix CI error, see: https://github.com/casbin/mongodb-adapter/actions/runs/15190141250/job/42720542625

[hsluoyz]

@slhmy this CI error happens after merging your PR: #68 . Can you help fix it?

[slhmy]

@slhmy this CI error happens after merging your PR: #68 . Can you help fix it?

Sure, I'll take a look.

[slhmy]

I think it's related with the low golang version in CI:

mongodb-adapter/.github/workflows/ci.yml

Line 20 in c1cb7f7

go-version: 1.14