[jesstaa]

You can make an io.Reader interface in any language. Interfaces don't really shine until you start composing them.

Say you have a type that implements the io.Reader, io.Writer, io.Closer and io.Seeker interfaces, eg. an os.File. This type would also automatically implement io.ReadCloser, io.WriteCloser, io.ReadWriter and io.ReadWriteCloser, io.ReadSeeker, io.ReadWriteSeeker, io.ReadWriteSeekerCloser, io.WriteSeeker, io.SeekCloser etc.

[MetaCosm]

Yeah, I simply think that this is hard to explain in a comment how useful and easy it is. But, I gave it my best Go...