truffle-config.js

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

const infuraKey = process.env.infura_key;
const mnemonic = process.env.mnemonic_key;
module.exports = {
  plugins: [
    'truffle-plugin-verify',
  ],
  api_keys: {
    etherscan: process.env.etherscan_key
  },

  networks: {
    development: {
     host: "127.0.0.1",
     port: 8545,
     network_id: "*",
    },

    proxy: {
     host: "127.0.0.1",
     port: 9545,
     network_id: "*",
    },

    live: {
      provider: () => new HDWalletProvider(mnemonic, `https://mainnet.infura.io/v3/${infuraKey}`),
      network_id: 1,
      gasPrice: 6000000001,
      skipDryRun: true
    },

    ropsten: {
      provider: () => new HDWalletProvider(mnemonic, `https://ropsten.infura.io/v3/${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 )
    },

    kovan: {
      provider: () => new HDWalletProvider(mnemonic, `https://kovan.infura.io/v3/${infuraKey}`),
      network_id: 42,       // kovan's id
      gas: 3716887,        // kovan 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: {
      version: "v0.6.2",
      settings: {
       optimizer: {
         enabled: true,
       },
       // evmVersion: "istanbul"
      }
    }
  }
}