truffle.js

require('dotenv').config();
const Web3 = require("web3");

const DEFAULT_GAS_WEI = 4600000;
const DEFAULT_ADDRESS_COUNT = 3;
const DEFAULT_ADDRESS_INDEX = 0;
const DEFAULT_GAS_GWEI_PRICE = "20";

const web3 = new Web3();
const HDWalletProvider = require("truffle-hdwallet-provider");

const addressCountValue = process.env["ADDRESS_COUNT_KEY"] || DEFAULT_ADDRESS_COUNT;
const mnemonicKeyValue = process.env["MNEMONIC_KEY"] || '';
const infuraKeyValue = process.env["INFURA_KEY"] || '';

if(infuraKeyValue === '' || mnemonicKeyValue === '') {
  console.log('WARNING: The infura key or/and mnemonic key are empty. They should not be empty.');
}

const gasKeyValue = process.env["GAS_WEI_KEY"] || DEFAULT_GAS_WEI;
const gasPriceKeyValue = process.env["GAS_PRICE_GWEI_KEY"] || DEFAULT_GAS_GWEI_PRICE;

module.exports = {
  web3: Web3,
  networks : {
    geth: {
      host: "localhost",
      port: 8045,
      network_id: "*"
    },
    ganache: {
      host: "127.0.0.1",
      port: 7545,
      network_id: "*"

    },
    infuraRinkeby: {
      provider: function() {
        return new HDWalletProvider(mnemonicKeyValue, `https://rinkeby.infura.io/${infuraKeyValue}`, DEFAULT_ADDRESS_INDEX, addressCountValue);
      },
      gas: gasKeyValue,
      gasPrice: web3.utils.toWei(gasPriceKeyValue, "gwei"),
      network_id: "5",
    },
    infuraKovan: {
      provider: function() {
        return new HDWalletProvider(mnemonicKeyValue, `https://kovan.infura.io/${infuraKeyValue}`, DEFAULT_ADDRESS_INDEX, addressCountValue);
      },
      gas: gasKeyValue,
      gasPrice: web3.utils.toWei(gasPriceKeyValue, "gwei"),
      network_id: "4",
    },
    infuraRopsten: {
      provider: function() {
        return new HDWalletProvider(mnemonicKeyValue, `https://ropsten.infura.io/${infuraKeyValue}`, DEFAULT_ADDRESS_INDEX, addressCountValue);
      },
      gas: gasKeyValue,
      gasPrice: web3.utils.toWei(gasPriceKeyValue, "gwei"),
      network_id: "3",
    },
    infuraMainnet: {
      provider: function () {
        return new HDWalletProvider(mnemonicKeyValue, `https://mainnet.infura.io/${infuraKeyValue}`, DEFAULT_ADDRESS_INDEX, addressCountValue);
      },
      gas: gasKeyValue,
      gasPrice: web3.utils.toWei(gasPriceKeyValue, "gwei"),
      network_id: "1",
    },
    infuraNet: {
      provider: function () {
        return new HDWalletProvider(mnemonicKeyValue, `https://infuranet.infura.io/${infuraKeyValue}`, DEFAULT_ADDRESS_INDEX, addressCountValue);
      },
      gas: gasKeyValue,
      gasPrice: web3.utils.toWei(gasPriceKeyValue, "gwei"),
      network_id: "2",
    }
  }
};