truffle-config.js

const path = require("path");
const HDWalletProvider = require("@truffle/hdwallet-provider");
const fs = require('fs');

const mnemonic = fs.readFileSync(".mnemonic").toString().trim();
const infuraKey = fs.readFileSync(".infura").toString().trim();

module.exports = {
  // See <http://truffleframework.com/docs/advanced/configuration>
  // to customize your Truffle configuration!
  contracts_build_directory: path.join(__dirname, "app/src/contracts"),
  networks: {
    develop: { // default with truffle unbox is 7545, but we can use develop to test changes, ex. truffle migrate --network develop
      host: "localhost",
      port: 8545,
      network_id: "*"
    },
    rinkeby: {
      provider: () => new HDWalletProvider(mnemonic, `https://rinkeby.infura.io/v3/${infuraKey}`),
      network_id: 4,       // Rinkeby's id
      gas: 5500000,        // Rinkeby has a lower block limit than mainnet
      confirmations: 2,
      timeoutBlocks: 200,
      skipDryRun: true,
      networkCheckTimeout: 10000000
    }
  },
  compilers: {
    solc: {
      optimizer: {
        enabled: true,
        runs: 200
      }
    }
  },
  solc: { optimizer: { enabled: true, runs: 200 } }
};