truffle.js

let HDWalletProvider = require("truffle-hdwallet-provider");
let Web3 = require("web3");

let provider = (endpoint) => {
    if (process.env.HDWALLET_MNEMONIC) {
        return new HDWalletProvider(process.env.HDWALLET_MNEMONIC, endpoint);
    } else {
        return new Web3.providers.HttpProvider(endpoint);
    }
}

module.exports = {
    networks: {
        local: {
            host: "127.0.0.1",
            port: 8545,
            network_id: "*" // Any network ID
        },
        localhd: {
            provider: () => provider("http://127.0.0.1:8545"),
            network_id: "*" // Any network ID
        },
        kovan: {
            gasPrice: 500000000,
            provider: () => provider("https://kovan.infura.io"),
            network_id: "42" // Kovan network ID
        },
    },
}