package main
import (
"fmt"
"os"
"io"
"log"
)
func main() {
in_file, err := os.Open("main.go")
if err != nil { log.Fatal(err) }
defer in_file.Close()
out_file, err := os.OpenFile("out.txt", os.O_RDWR|os.O_CREATE, 0644)
if err != nil { log.Fatal(err) }
defer out_file.Close()
n, err := io.Copy(out_file, in_file)
if err != nil { log.Fatal(err) }
fmt.Println("read n bytes", n)
}