var _ … type fileOnDisk … // Close closes a file. func (f *fileOnDisk) Close() error { … } // Read reads a file's content. func (f *fileOnDisk) Read(p []byte) (n int, err error) { … } // Write writes bytes to a file func (f *fileOnDisk) Write(p []byte) (n int, err error) { … } // Stat returns an interface which has all the information regarding the file. func (f *fileOnDisk) Stat() (os.FileInfo, error) { … }