How to post FormData using http package in Flutter, with multiple file with multiple key?

Question

I have to Post Multipart Data using http package with multiple files with "files" key, every file have own "files" key like bellow.

here entityDTOString is data and files are files which is picked, If I pick 3 files then there is 3 files key and values.

below is Form Data,

entityDTOString: {....}
files: (binary)
files: (binary)

And The raw data as below like.

------WebKitFormBoundaryAscKwsX2IZgxxKpY
Content-Disposition: form-data; name="entityDTOString"

{"key":value...}
------WebKitFormBoundaryAscKwsX2IZgxxKpY
Content-Disposition: form-data; name="files"; filename="file.png"
Content-Type: image/png


------WebKitFormBoundaryAscKwsX2IZgxxKpY
Content-Disposition: form-data; name="files"; filename="file.pdf"
Content-Type: application/pdf


------WebKitFormBoundaryAscKwsX2IZgxxKpY--

So please can anyone help me how I can do this.