text: var HDWalletProvider = require("@truffle/hdwallet-provider");
  const mnemonic = "";
  const walletChildNum = 0;
  const networkAddress = "https://mainnet.infura.io/v3/<your-api-key>";
  const ropstenNetworkAddress = "https://ropsten.infura.io/v3/<your-api-key>";
  
  module.exports = {
    // See <http://truffleframework.com/docs/advanced/configuration>
    // to customize your Truffle configuration!
    networks: {
      development: {
        host: '127.0.0.1',
        port: 8545, // ganache-cli
        network_id: '*', // Match any network id
        gas: 6700000,
        gasPrice: 0x01
      },
      coverage: {
        host: 'localhost',
        network_id: '*',
        port: 8321,
        gas: 10000000000000,
        gasPrice: 0x01
      },
      ropsten: {
        network_id: 3,
        provider: function() {
          return new HDWalletProvider(mnemonic, ropstenNetworkAddress, walletChildNum)
        },
        // ropsten block limit
        gas: 4700000,
        gasPrice: 0x01
      },
      mainnet: {
        network_id: 1,
        provider: function () {
          return new HDWalletProvider(mnemonic, networkAddress, walletChildNum)
        },
      },
    },
    compilers: {
      solc: {
        version: "v0.4.24+commit.e67f0147"  // ex:  "0.4.20". (Default: Truffle's installed solc)
      }
    },
    solc: {
      optimizer: {
        enabled: true,
        runs: 200
      }
    }
  };
  