Vue 2.0 3.0 configuration forwarding

We configured forwarding vue3.0 is new vue.config.jsin the configuration (and package.jsonsimilar)
today when writing code using 2.0, 500 error has been forwarded unsuccessful
forward 2.0 project is bulid文件夹下 webpack.base.conf.jswell equipped with:

3.0 in the new file vue.config.js;