truffle-config.js

const HDWalletProvider = require('truffle-hdwallet-provider')
require('dotenv').config()
const mnemonic = process.env.HDWALLET_MNEMONIC
console.log(process.env.INFURA_API_KEY)
console.log(mnemonic)
module.exports = {
  migrations_directory: "./migrations",
  networks: {
    development: {
      host: "localhost",
      port: 8545,
      network_id: "*" // Match any network id
    },
    mainnet: {
      provider: function() {
        return new HDWalletProvider(mnemonic, "https://mainnet.infura.io/v3" + process.env.INFURA_API_KEY)
     },
     network_id: 1,
     gasPrice: 2000000000,
     gas: 6000000
      //gas: 4000000,
      //gasPrice: 2892111612
    },
    ropsten: {
      provider: new HDWalletProvider(process.env.MNENOMIC, "https://ropsten.infura.io/v3/" + process.env.INFURA_API_KEY),
      network_id: 3
      //gas: 4000000,
      //gasPrice: 28921116127
    },
    rinkeby: {
      provider: new HDWalletProvider(mnemonic, "https://rinkeby.infura.io/v3/" + process.env.INFURA_API_KEY),
      network_id: 4
      //gas: 6000000,
      //gasPrice: 28921116127
    },
    kovan: {
      provider: new HDWalletProvider(mnemonic, "https://kovan.infura.io/v3/" + process.env.INFURA_API_KEY),
      network_id: 42
      //gas: 4612388,
      //gasPrice: 28921116127
    },
    coverage: {
      host: "localhost",
      network_id: "*",
      port: 8555,         // <-- If you change this, also set the port option in .solcover.js.
      gas: 0xfffffffffff, // <-- Use this high gas value
      gasPrice: 0x01      // <-- Use this low gas price
    },
  },
  solc: {
    optimizer: {
      enabled: true,
      runs: 500
    }
  } 
};