// ... reused here also. No need to allocate an extra buffer.
	if _, err := io.CopyBuffer(os.Stdout, r2, buf); err != nil {
		log.Fatal(err)
	}

	// Output:
	// first reader
	// second reader
}

func ExampleCopyN() {
	r := strings.NewReader("some io.Reader stream to be read")

	if _, err := io.CopyN(os.Stdout, r, 4); err != nil {
		log.Fatal(err)
	}

	// Output:
	// some
}

func ExampleReadAtLeast() {