$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 8.8.1
$ cabal --version
cabal-install version 3.0.0.0
compiled using version 3.0.0.0 of the Cabal library
$ cabal v2-update
Config file path source is default config file.
Config file /root/.cabal/config not found.
Writing default configuration to /root/.cabal/config
Downloading the latest package list from hackage.haskell.org
$ cabal v2-install pandoc
Resolving dependencies...
cabal: Could not resolve dependencies:
[__0] trying: pandoc-2.7.3 (user goal)
[__1] trying: http-client-tls-0.3.5.3 (dependency of pandoc)
[__2] trying: tls-1.5.1 (dependency of http-client-tls)
[__3] trying: x509-validation-1.6.11 (dependency of tls)
[__4] trying: asn1-encoding-0.9.5 (dependency of tls)
[__5] next goal: base (dependency of pandoc)
[__5] rejecting: base-4.13.0.0/installed-4.1... (conflict: asn1-encoding =>
base>=3 && <4.13)
[__5] rejecting: base-4.12.0.0, base-4.11.1.0, base-4.11.0.0, base-4.10.1.0,
base-4.10.0.0, base-4.9.1.0, base-4.9.0.0, base-4.8.2.0, base-4.8.1.0,
base-4.8.0.0, base-4.7.0.2, base-4.7.0.1, base-4.7.0.0, base-4.6.0.1,
base-4.6.0.0, base-4.5.1.0, base-4.5.0.0, base-4.4.1.0, base-4.4.0.0,
base-4.3.1.0, base-4.3.0.0, base-4.2.0.2, base-4.2.0.1, base-4.2.0.0,
base-4.1.0.0, base-4.0.0.0, base-3.0.3.2, base-3.0.3.1 (constraint from
non-upgradeable package requires installed instance)
[__5] fail (backjumping, conflict set: asn1-encoding, base, pandoc)
Backjump limit reached (currently 4000, change with --max-backjumps or try to
run with --reorder-goals).