ghc-mod doesn't yet support GHC 8.2 or later. You'll need to use an older version of the compiler if you want ghc-mod support. If you check out ghc-mod's Stackage page, you can see that the latest snapshots supporting it are lts-8.24 and nightly-2017-06-28, so those are options if you need ghc-mod support. Note, however, that they're relatively old, so may be missing other things you want.
I wrote a blog post recently about selecting older snapshots for building tools, which may be helpful.