truffle-config.js

const HDWalletProvider = require("@truffle/hdwallet-provider");
//
// const fs = require('fs');
// const mnemonic = fs.readFileSync(".secret").toString().trim();

const MNEMONIC =
  process.env.MNEMONIC ||
  "";

module.exports = {
  /**
   * Networks define how you connect to your ethereum client and let you set the
   * defaults web3 uses to send transactions. If you don't specify one truffle
   * will spin up a development blockchain for you on port 9545 when you
   * run `develop` or `test`. You can ask a truffle command to use a specific
   * network from the command line, e.g
   *
   * $ truffle test --network <network-name>
   */

  networks: {
    root: {
      provider: () =>
        new HDWalletProvider(
          MNEMONIC,
          `https://goerli.infura.io/v3/5687b932e64441e5a297a0bfba8895cd`
        ),
      network_id: 5,
      gas: 7000000,
      gasPrice: 10000000000, // 10 gwei
      skipDryRun: true,
    },
    child: {
      provider: () =>
        new HDWalletProvider(MNEMONIC, "https://rpc-mumbai.matic.today"),
      network_id: 80001,
      gas: 7000000,
      gasPrice: 10000000000, // 10 gwei
      skipDryRun: true,
    },
  },

  // Configure your compilers
  compilers: {
    solc: {
      version: "0.6.6", // Fetch exact version from solc-bin (default: truffle's version)
      docker: true, // Use "0.5.1" you've installed locally with docker (default: false)
      parser: "solcjs",
      settings: {
        // See the solidity docs for advice about optimization and evmVersion
        // optimizer: {
        //   enabled: false,
        //   runs: 200
        // }
        evmVersion: "constantinople",
      },
    },
  },
};