Example package using
go build and then the built binary. Note the error. Now run
go generate. Note the new file in the repo. Feel free to look at it's
go build again and then run the built binary.
By the way, setting a string like this with
go generate is probably overkill,
go build -ldflags "-X 'main.compiledAt=whatever'" would do that more
simply, but there are times when that isn't an option, or when the structure
being generated is more complex than a simple string.