truffle-config.js

require('dotenv').config()
const path = require("path")
const mnemonic = process.env.MNENOMIC
const HDWalletProvider = require("truffle-hdwallet-provider")

module.exports = {
  networks: {
    development: {
      host: "127.0.0.1",
      port: 8545,
      network_id: "*",
    },
    ropsten: {
      provider: () =>
        new HDWalletProvider(
          mnemonic,
          'https://ropsten.infura.io/v3/' + process.env.INFURA_API_KEY
        ),
      network_id: '3',
      gas: 4465030,
      gasPrice: 10000000000,
    },
    kovan: {
      provider:() =>
        new HDWalletProvider(
          mnemonic,
          'https://kovan.infura.io/v3/' + process.env.INFURA_API_KEY
        ),
      network_id: '42',
      gas: 4465030,
      gasPrice: 10000000000,
    },
    rinkeby: {
      provider: () =>
        new HDWalletProvider(
          process.env.MNENOMIC,
          "https://rinkeby.infura.io/v3/" + process.env.INFURA_API_KEY
        ),
      network_id: 4,
      gas: 3000000,
      gasPrice: 10000000000
    },
    // main ethereum network(mainnet)
    main: {
      provider: () =>
        new HDWalletProvider(
          process.env.MNENOMIC,
          "https://mainnet.infura.io/v3/" + process.env.INFURA_API_KEY
        ),
      network_id: 1,
      gas: 3000000,
      gasPrice: 10000000000
    }
  },
  compilers: {
    solc: {
      version: "0.5.0"
    }
  }
};