(b) looking at a whole slew of OTHER Go projects, including those outside of the directory within which I was running the command, namely : -
Now, of course, note what I did previously i.e. rm go.mod
THAT WAS MY DOWNFALL :-)
From this: -
Why does 'go mod tidy' record indirect and test dependencies in my 'go.mod'?
go mod tidy updates your current go.mod to include the dependencies needed for tests in your module — if a test fails, we must know which dependencies were used in order to reproduce the failure.
Guess what I didn't have ?
So, the key was to re-create go.mod via: -
go mod init
and then re-run the make command that had initially populated go.mod - which also ran go mod tidy and then ... everything is OK.