Something like this will hopefully get the point across on how to handle "multipart/form-data" forms. It will print the content of the upload to the server's stdout.

https://play.golang.org/p/DiNGdl27kE

You can use curl to test it out (it assumes a file called "foobar.txt" is available):

    curl -v -F upload=@foobar.txt localhost:8080/upload

I actually wrote an extremely shonky/basic file upload thing and contributed it to the weird 'illacceptanything' repository, while that was a thing, about a year and a half ago.

Maybe you'll find it helpful, maybe not. Ignore the bindata.go stuff and look at main.go (inc. file accepting) & the file upload control (w/Bootstrap fileinput.min.js) & the braindead simple HTML templating stuff.

https://github.com/leafi/illacceptanything/commit/1b78922f89...

I don't know much about Go so can't speak to the server-side handling of file uploads. The drag/drop side of things is server agnostic - I strongly recommend http://www.dropzonejs.com

This might be more of a complete app than you need, but https://transfer.sh is open source and it looks fairly compact. Could be some interesting examples in there?

I really like the gophish app for easy to understand common patterns in web apps.