mime.go
func New(filename string, utf8 bool) *Reader {
	return &Reader{filename, utf8, nil, sync.Mutex{}}
}
func New(filename string, utf8 bool) *Reader {
	return &Reader{filename, utf8, nil, sync.Mutex{}}
}
// New creates a new Reader. The filename is a list of mimetypes and extensions.
// If utf8 is true, "; charset=utf-8" will be added when setting http headers.