#### KNEXFILE:

module.exports = {
    development: {
      client: process.env.DB_CLIENT,
      connection: process.env.DB_CONNECTION,
      migrations: {
          directory: process.env.DB_MIGRATION_DIR,
      },
      seeds: {
          directory: process.env.DB_SEEDS_DIR
      },
      useNullAsDefault: true
    },

    production: {
      client: process.env.DB_CLIENT,
      connection: process.env.DB_CONNECTION,
      migrations: {
          directory: process.env.DB_MIGRATION_DIR,
      },
      seeds: {
          directory: process.env.DB_SEEDS_DIR
      },
      useNullAsDefault: true
    }

};



######### demonstrating environment properties are setup--
#checking .env file for properties:

$ node
>  process.env.DB_CLIENT
'postgresql'

> const dotenv = require('dotenv').config();
undefined
> dotenv
{ parsed:
   { NODE_ENV: 'production',
     DB_CLIENT: 'postgresql',
     DB_CONNECTION: 'postgres://pat:secret@localhost:5432/timetracker',
     DB_MIGRATION_DIR: './db/migrations',
     DB_SEEDS_DIR: './db/seeds' } }

#### problem code:
const dotenv = require('dotenv').config();
const knex = require('knex');
const environment = process.env.NODE_ENV;
const knex_config = require('./knexfile')[environment];
const database = require('knex')(knex_config);

# CAUSES ERROR:
TypeError: Cannot read property 'client' of undefined
    at Knex (/home/pat/apps/timetracker/node_modules/knex/lib/index.js:49:41)


FROM KNEX SOURCE FILE FILE -- ASTERISKS == LINE 49
// The client names we'll allow in the `{name: lib}` pairing.
var aliases = {
  'mariadb': 'maria',
  'mariasql': 'maria',
  'pg': 'postgres',
  'postgresql': 'postgres',
  'sqlite': 'sqlite3'
};

function Knex(config) {
  if (typeof config === 'string') {
    return new Knex((0, _assign3.default)((0, _parseConnection2.default)(config), arguments[2]));
  }
  var Dialect = void 0;
  if (arguments.length === 0 || !config.client && !config.dialect) { // ************* LINE 49 *************
    Dialect = _client2.default;
  } else if (typeof config.client === 'function' && config.client.prototype instanceof _client2.default) {
    Dialect = config.client;
  } else {
    var clientName = config.client || config.dialect;
    Dialect = require('./dialects/' + (aliases[clientName] || clientName) + '/index.js');
  }
  if (typeof config.connection === 'string') {
    config = (0, _assign3.default)({}, config, { connection: (0, _parseConnection2.default)(config.connection).connection });
  }
  return (0, _makeKnex2.default)(new Dialect(config));
}