Bump all build go versions to v1.21.0
Bump the minimum build package version to v1.19.0
Debian "buster" is not longer supported. Security updates have been
discontinued since June 30th 2022. We will build using the latest
version, "bookworm".
In this commit, we rename the previously unexported ticker into T,
making it exported along the way. This is nice as we now have access to
the actual interface implementation without the need of making further
type assertions.
This commit adds a Mock Ticker, implementing the
Ticker interface. The ticker abides by the
behavioral requirements of the production
implementation, but also includes the ability to
force feed ticks while the Ticker is paused.
This commit also places the mock.go file behind
the debug build flag. This allows us to import
the MockTicker into our unit tests.
