example

example.go

package main

import (
	"fmt"
	"io"
	"os"
)

func main() {
	var count int64
	var total int64
	var err error

	for {
		count, err = io.CopyN(os.Stdout, os.Stdin, 1048576)
		if err != nil {
			total += count
			goto DONE
		}
		total += count
	}

DONE:
	_, _ = fmt.Fprintf(os.Stderr, "%d bytes copied.\n", total)
}