truffle.js

const fs = require('fs');
const HDWalletProvider = require('truffle-hdwallet-provider');
// const infuraKey = fs.readFileSync("infura").toString().trim();
// const mnemonic = fs.readFileSync("secret").toString().trim();

const infuraKey = process.env.INFURA;
const mnemonic = process.env.MNEMONIC;

module.exports = {

  networks: {

    development: {
     host: "127.0.0.1",     // Localhost (default: none)
     port: 8545,            // Standard Ethereum port (default: none)
     network_id: "*",       // Any network (default: none)
    },

    // Useful for deploying to a public network.
    // NB: It's important to wrap the provider as a function.
    ropsten: {
      provider: () => new HDWalletProvider(mnemonic, `https://ropsten.infura.io/${infuraKey}`),
      network_id: 3,       // Ropsten's id
      gas: 5500000,        // Ropsten has a lower block limit than mainnet
      confirmations: 2,    // # of confs to wait between deployments. (default: 0)
      timeoutBlocks: 200,  // # of blocks before a deployment times out  (minimum/default: 50)
      skipDryRun: true     // Skip dry run before migrations? (default: false for public nets )
    },
  },

  // Set default mocha options here, use special reporters etc.
  mocha: {
    // timeout: 100000
  },

  // Configure your compilers
  compilers: {
    // solc: {
    //   settings: {
    //     optimizer: {
    //       enabled: true, // Default: false
    //       runs: 200      // Default: 200
    //     },
    //   }
    // }
  }

}