Content-Type change to 'text/plain' when build the app in windows

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Issue Details

Electron Version: 6.0.11
Operating System: Windows 10 (1803)

Expected Behavior

I wrote an application that send post request with FormData or Json to Flask python server. When in developer mode, the request is always successful with header : "multipart/formdata" or "application/json".

Actual Behavior

But when I build the app with electron-builder , yarn dist, the request fails because the header is only "text/plain" that the Flask server couldn't parse the data.

To Reproduce

My application was written with Reactjs and I first try fetch in React but it failed. I aslo used ipcRenderer, ipcMan to handle the request but it only ran correctly on dev mode.

Is it a problem about CORs or something like that which happens when packing app ?

electron / electron