Get the mime type / content type of a file from its extension without external dependencies

go get github.com/cubewise-code/go-mime

import (
  "github.com/cubewise-code/go-mime"
)

// Get the file extension
ext := filepath.Ext(fileName)
// An empty string is returned if the extension is not found
contentType := gomime.TypeByExtension(ext)

We wanted a simple mime library that gives a consistent result on each environment. The golang mime package (https://golang.org/pkg/mime/) loads the list of mime types using the OS, meaning you get a different list depending on OS and OS version. On Windows this depends on the programs installed and whether the user running the process has access to the registry.

The mime list are sourced from here: https://github.com/micnic/mime.json