Postgres in Nix shell

shell.nix

with import <nixpkgs> {};
let
  pg_root = builtins.toString ./. + "/.postgres";
  pg_user = "postgres";
  pg_db = "service";
  pg_bind = "127.0.0.1";

  svc_pg_user = "dev";
  svc_pg_password = "changeme";

in mkShell {
  name = "fsharp-stub-service";

  buildInputs = [
    postgresql
  ];

  shellHook = ''
    export PGDATA=${pg_root}/data
    export PGHOST=${pg_root}/postgres
    export PGLOG=$PGHOST/pg.log

    function cleanup_pg {
      echo "Stopping DB..."
      pg_ctl stop
      echo "Destroying DB..."
      rm -rf "${pg_root}"
    }

    trap cleanup_pg EXIT

    if [ ! -d ${pg_root} ]; then
      mkdir -p $PGHOST
      mkdir -p $PGDATA

      echo "Initialising DB..."
      initdb $PGDATA --auth=trust --auth-host=trust > "${pg_root}/db-init.log" 2>&1
      echo "Starting server..."
      pg_ctl start -l $PGLOG -o '-c listen_addresses= -c unix_socket_directories=$PGHOST'
      createuser -s ${svc_pg_user}
      createdb ${pg_db} -O ${svc_pg_user}
    fi
  '';
}