update go.mod to 1.17

[codyoss]

By declaring 1.17 we enable downstream consumers this module to
take advantage of mod graph pruning and lazy loading of modules. We
still support older versions, but this is just nice for our users
that are declaring a newer version in their module.

We should eventually roll this out to the other libs we maintain too as only mods with 1.17 can be pruned.