.babelrc

{
  "plugins": [
    "syntax-async-functions",
    "transform-decorators-legacy",
    "transform-class-properties",
    "transform-object-rest-spread",
    "transform-react-jsx",
    "transform-flow-strip-types"
  ]
}

package.json

{
  "name": "mizchi-new-proj",
  "version": "1.0.0",
  "main": "index.js",
  "author": "Koutarou Chikuba <miz404@gmail.com>",
  "license": "MIT",
  "dependencies": {
    "babel-core": "^6.21.0",
    "babel-loader": "^6.2.10",
    "babel-plugin-syntax-async-functions": "^6.13.0",
    "babel-plugin-transform-class-properties": "^6.19.0",
    "babel-plugin-transform-decorators-legacy": "^1.3.4",
    "babel-plugin-transform-flow-strip-types": "^6.21.0",
    "babel-plugin-transform-object-rest-spread": "^6.20.2",
    "babel-plugin-transform-react-jsx": "^6.8.0",
    "webpack": "2.1.0-beta.25",
    "webpack-async-await": "^1.1.0"
  }
}

webpack.config.js

const webpack = require('webpack');
const AsyncAwaitPlugin = require('webpack-async-await') ;

module.exports = {
  entry: './src/main.js',
  output: {
    path: "public",
    filename: 'bundle.js'
  },
  plugins: [
    new AsyncAwaitPlugin({})
  ],
  module: {
    rules: [
      {
        test: /\.js$/,
        use: 'babel-loader',
        exclude: /node_modules/
      }
    ]
  }
};