Load a Solana keypair from a .env file as a byte array

load.js

// "@solana/web3.js": "^1.87.6",
import { Connection, Keypair, clusterApiUrl } from '@solana/web3.js';
import dotenv from 'dotenv';
dotenv.config();

const connection = new Connection(clusterApiUrl('devnet'), 'confirmed');

const payerSecretKey = JSON.parse(process.env.PAYER);
const payer = Keypair.fromSecretKey(Uint8Array.from(payerSecretKey));

if (!payer) {
  throw new Error('PAYER is not set')
}

console.log('Payer address:', payer.publicKey.toBase58());
console.log("Payer Account Balance:", await connection.getBalance(payer.publicKey));