code: func readMimetypes(filename string) (map[string]string, error) {
  	mimetypes := make(map[string]string)
  	// Read the mimetype file
  	data, err := ioutil.ReadFile(filename)
  	if err != nil {
  		return nil, err
  	}
  	// For each line, store extensions and mimetypes in the hash map
  	for _, line := range bytes.Split(data, []byte("\n")) {
  		fields := bytes.Fields(line)
  		if len(fields) > 1 {
  			for _, ext := range fields[1:] {
  				mimetypes[string(ext)] = string(fields[0])
  			}
  		}
  	}
  	return mimetypes, nil
  }
docs: // Read a mimetype text file. Return a hash map from ext to mimetype.