Update Go modules

[SuperQ]

Update Go module dependencies to latest releases.

• Update Go minimum version to 1.11 to satisfy xerrors requirement.

[matttproud]

I am planning on retiring the v1 branch (unless someone gives me a very good reason). v1 will remain, though. I'm a bit concerned about extra churn there. The last time we updated the respective libraries in v1, it resulted in considerable global breakage. I suspect it's harmless to leave these dependencies pinned as-is. Are there several known reasons why the dependencies in v1 need to be updated?

[SuperQ]

Updating the dependency versions, without changing which library, is a standard thing to do in Go modules. It signals to downstream Go module users to update their transitive dependencies.

In this case, we're not changing the library fully like was done for v2. We're only updating the existing library, which is backwards compatible.

However, I would suggest we publish the retract change first, so that I can apply Go 1.16 formatting.