truffle-config.js

require('dotenv').config()
const HDWalletProvider = require('truffle-hdwallet-provider-privkey')


const PRIVATE_KEY = process.env.PRIVATE_KEY
const API_URL = process.env.API_URL

module.exports = {
 
  networks: {
    // Useful for testing. The `development` name is special - truffle uses it by default
    // if it's defined here and no other network is specified at the command line.
    // You should run a client (like ganache-cli, geth or parity) in a separate terminal
    // tab if you use this network and you must also set the `host`, `port` and `network_id`
    // options below to some value.
    //
       development: {
        host: "127.0.0.1",     // Localhost (default: none)
        port: 8545,            // Standard Ethereum port (default: none)
        network_id: "*",       // Any network (default: none)
     },

     rinkeby: {
        provider: function() {
          return new HDWalletProvider(
            //private key
            [PRIVATE_KEY],
            //url to an ethereum node
            API_URL
          )
        },

        network_id: 4
     }
   
  },

  // Set default mocha options here, use special reporters etc.
  mocha: {
    // timeout: 100000
  },

  // Configure your compilers
  compilers: {
    solc: {
      version: "0.8.10",    // Fetch exact version from solc-bin (default: truffle's version)
      // docker: true,        // Use "0.5.1" you've installed locally with docker (default: false)
      // settings: {          // See the solidity docs for advice about optimization and evmVersion
      //  optimizer: {
      //    enabled: false,
      //    runs: 200
      //  },
      //  evmVersion: "byzantium"
      // }
    }
  },

  // Truffle DB is currently disabled by default; to enable it, change enabled:
  // false to enabled: true. The default storage location can also be
  // overridden by specifying the adapter settings, as shown in the commented code below.
  //
  // NOTE: It is not possible to migrate your contracts to truffle DB and you should
  // make a backup of your artifacts to a safe location before enabling this feature.
  //
  // After you backed up your artifacts you can utilize db by running migrate as follows: 
  // $ truffle migrate --reset --compile-all
  //
  // db: {
    // enabled: false,
    // host: "127.0.0.1",
    // adapter: {
    //   name: "sqlite",
    //   settings: {
    //     directory: ".db"
    //   }
    // }
  // }
};