truffle.js

const HDWalletProvider = require("truffle-hdwallet-provider")
const fs = require("fs")

// first read in the secrets.json to get our mnemonic
let secrets
let mnemonic
if(fs.existsSync("secrets.json")) {
  secrets = JSON.parse(fs.readFileSync("secrets.json", "utf8"))
  mnemonic = secrets.mnemonic
} else {
  console.log("no secrets.json found. You can only deploy to the testrpc.");
  mnemonic = "" 
}

module.exports = {
  networks: {
    development: {
      host: "localhost",
      port: 8545,
      network_id: "*" // Match any network id
    },
    kovan: {
      provider: new HDWalletProvider(mnemonic, "https://kovan.infura.io"),
      network_id: "*",
      gas: 4500000,
      gasPrice: 25000000000
    },
    rinkeby: {
      provider: new HDWalletProvider(mnemonic, "https://rinkeby.infura.io"),
      network_id: "*",
      gas: 4500000,
      gasPrice: 25000000000
    },
    mainnet: {
      provider: new HDWalletProvider(mnemonic, "https://mainnet.infura.io"),
      network_id: 1,
      gas: 4500000,
      gasPrice: 4000000000
    }
  }
};