By default, socat only waits 0.5s for the remote side to finish after
getting EOF on the local side. So don't close the local side, instead
wait for socat to exit when the remote side finishes.
http://hydra.nixos.org/build/10663282
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
