make fs dynamic loading

Author: billbsing

src/KeyPair.ts

@@ -5,7 +5,6 @@
 
 */
 
-import fs from 'fs'
 import { KeyObject, generateKeyPairSync, createPrivateKey, createPublicKey, randomBytes, sign } from 'crypto'
 import pem from 'pem-file'
 
@@ -91,6 +90,8 @@ export class KeyPair {
      *
      */
     public static async importFromFile(filename: string, password: string): Promise<KeyPair> {
+
+	const fs = await import('fs')
         if (fs.existsSync(filename)) {
             const data = await fs.promises.readFile(filename)
             return KeyPair.importFromString(data.toString(), password)
@@ -124,6 +125,7 @@ export class KeyPair {
      *
      */
     public async exportToFile(filename: string, password: string): Promise<unknown> {
+	const fs = await import('fs')
         return await fs.promises.writeFile(filename, this.exportToString(password))
     }