@vrom911 to be honest I couldn't really tell what goes wrong on Windows - locally I recognize that qualified imports didn't seem to work in the tests.

src\Colog\Message.hs:422: failure in expression `showTime $ C.Time 1577656800000000000'
expected: "[29 Dec 2019 22:00:00.000 +00:00] "
 but got:
          ^
          <interactive>:27:12: error:
              Not in scope: data constructor `C.Time'
              NB: no module named `C' is imported.

But also after using full names in the test code it didn't worked; also I believe this might be triggered by some change in ghci, but I haven't found a corresponding issue on the GHC issue tracker. So I just added a generell comment why doctest is disabled on windows. However I believe this shouldn't be a problem, since I think we are good enough if all tests pass on linux systems 😉