truffle-config.js

/**
 * Use this file to configure your truffle project. It's seeded with some
 * common settings for different networks and features like migrations,
 * compilation and testing. Uncomment the ones you need or modify
 * them to suit your project as necessary.
 *
 * More information about configuration can be found at:
 *
 * truffleframework.com/docs/advanced/configuration
 *
 * To deploy via Infura you'll need a wallet provider (like truffle-hdwallet-provider)
 * to sign your transactions before they're sent to a remote public node. Infura API
 * keys are available for free at: infura.io/register
 *
 * You'll also need a mnemonic - the twelve word phrase the wallet uses to generate
 * public/private key pairs. If you're publishing your code to GitHub make sure you load this
 * phrase from a file you've .gitignored so it doesn't accidentally become public.
 *
 */

const path = require("path");
var HDWalletProvider = require("truffle-hdwallet-provider");
require('dotenv').config()

module.exports = {
  /**
   * Networks define how you connect to your ethereum client and let you set the
   * defaults web3 uses to send transactions. If you don't specify one truffle
   * will spin up a development blockchain for you on port 9545 when you
   * run `develop` or `test`. You can ask a truffle command to use a specific
   * network from the command line, e.g
   *
   * $ truffle test --network <network-name>
   */

  networks: {

     // main ethereum network(mainnet)
     main: {
       provider: () => new HDWalletProvider(process.env.MNEMONIC, "https://mainnet.infura.io/"),
       network_id: 1,
       gas: 4465030,
       gasPrice: 21
     },

     ropsten: {
       provider: () => new HDWalletProvider(process.env.MNEMONIC, "https://ropsten.infura.io/"),
       network_id: 3,
       gas: 3500000
     },

    kovan: {
       provider: () => new HDWalletProvider(process.env.MNEMONIC, "https://kovan.infura.io/"),
       network_id: 42,
       gas: 3500000
    },

    rinkeby: {
       provider: () => new HDWalletProvider(process.env.MNEMONIC, "https://rinkeby.infura.io/"),
       network_id: 4,
       gas: 6985121
    }
  },

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

  // Configure your compilers
  compilers: {
    solc: {
      version: "0.5.4",    // Fetch exact version from solc-bin (default: truffle's version)
      // docker: true,        // Use "0.5.1" you've installed locally with docker (default: false)
      settings: {          // See the solidity docs for advice about optimization and evmVersion
       optimizer: {
         enabled: true,
         runs: 200
       },
      //  evmVersion: "byzantium"
      }
    }
  },

  // See <http://truffleframework.com/docs/advanced/configuration>
  // to customize your Truffle configuration!
  contracts_build_directory: path.join(__dirname, "client/src/contracts")
}