bytenode: SyntaxError: Unexpected identifier

I used bytenode -c index.js , the following error occurred:

evalmachine.<anonymous>:1 (function (exports, require, module, __filename, __dirname) { import Koa from ‘koa’; ^^^

SyntaxError: Unexpected identifier at new Script (vm.js:74:7) at compileCode (/usr/local/lib/node_modules/bytenode/index.js:28:16) at Object.compileFile (/usr/local/lib/node_modules/bytenode/index.js:147:22) at /usr/local/lib/node_modules/bytenode/cli.js:47:18 at Array.forEach (<anonymous>) at Object.<anonymous> (/usr/local/lib/node_modules/bytenode/cli.js:38:17) at Module._compile (internal/modules/cjs/loader.js:702:30) at Object.Module._extensions…js (internal/modules/cjs/loader.js:713:10) at Module.load (internal/modules/cjs/loader.js:612:32) at tryModuleLoad (internal/modules/cjs/loader.js:551:12)

How can I solve this problem? thanks.