Go 1.16 has file embedding built-in, you should use that!

Staticfiles allows you to embed a directory of files into your Go binary. It is optimized for performance and file size, and automatically compresses everything before embedding it. Here are some of its features:

• Compresses files, to make sure the resulting binary isn't bloated. It only compresses files that are actually smaller when gzipped.
• Serves files gzipped (while still allowing clients that don't support it to be served).
• Ignores hidden files (anything that starts with .).
• Fast. The command-line tool reads and compresses files in parallel, and the resulting Go file serves files very quickly, avoiding unnecessary allocations.
• No built-in development mode, but makes it very easy to implement one (see local development mode).

It has some clever tricks, like only compressing a file if it actually makes the binary smaller (PNG files won't be compressed, as they already are and compressing them again will make them bigger).

I recommend creating a separate package inside your project to serve as the container for the embedded files.

For an example of how to use the resulting package, check out example/example.go. You can also see the API it generates at godoc.org.

Install with

go get bou.ke/staticfiles

Simply run the following command (it will create the result directory if it doesn't exist yet):

staticfiles -o files/files.go static/

I recommend putting it into a Makefile as follows:

files/files.go: static/*
	staticfiles -o files/files.go static/

The staticfiles command accept the following arguments:

--build-tags string
      Build tags to write to the file
-o string
      File to write results to. (default "staticfiles.go")
--package string
      Package name of the resulting file. Defaults to name of the resulting file directory

While Staticfiles doesn't have a built-in local development mode, it does support build tags which makes implementing one very easy. Simply run staticfiles with --build-tags="!dev" and add a file in the same directory that implements the same API, but with //+build dev at the that and using http.FileServer under the hood. You can find an example in files/files_dev.go. Once you have that set up you can simply do go build --tags="dev" to compile the development version. In the way I set it up, you could even do go build --tags="dev" -ldflags="-X bou.ke/staticfiles/files.staticDir=$(pwd)/static" to set the static file directory to a specific path.

The resulting file will contain the following functions and variables:

ServeHTTP will attempt to serve an embedded file, responding with gzip compression if the clients supports it and the embedded file is compressed.

Open allows you to read an embedded file directly. It will return a decompressing Reader if the file is embedded in compressed format. You should close the Reader after you're done with it.

ModTime returns the modification time of the original file. This can be useful for caching purposes.

NotFound is used to respond to a request when no file was found that matches the request. It defaults to http.NotFound, but can be overwritten.

Server is simply ServeHTTP but wrapped in http.HandlerFunc so it can be passed into net/http functions directly.