My first Go program. Hash a file using a buffered reader

sha.go

package main

/**
* Help from:
* http://stackoverflow.com/questions/1821811/how-to-read-write-from-to-file
* https://groups.google.com/forum/#!topic/golang-nuts/1mc64pj_S50
*  http://pastebin.com/DgurHbpe
**/

import (
    "io"
    "bufio"
    "os"
    "flag"
    "log"
    "crypto/sha1"
    "encoding/hex"
)

var file * string = flag.String("file", "", "File to hash")

func main() {
    flag.Parse()
    log.Println("Opening file: " + *file)
    
    // Open a file handle and check for errors
    fi, err := os.Open(*file)
    if err != nil {
        panic(err)
    }

    // Whenever we're done just close the file for us
    defer func() {
        // When we close the file check for errors too
        err := fi.Close()
        if err != nil {
            panic(err)
        }
    }()

    // Opened a buffered reader
    r := bufio.NewReader(fi)

    // Setup hasher
    hasher := sha1.New()

    // We're going to read the file in 4KB chunks
    buf := make([]byte, 1024*4)

    log.Println("Reading file ...")
    for {
        // log.Println("Reading data ...")

        // Read the file, check for errors (except EOF)
        n, err := r.Read(buf)
        if err != nil && err != io.EOF {
            panic(err)
        }

        // If there are 0 bytes left break from the loop
        if n == 0 {
            break
        }

        // Write to the hasher
        _, err = hasher.Write(buf[:n])
        if err != nil {
            panic(err)
        }
    }

    // Output the sha
    log.Println(hex.EncodeToString(hasher.Sum(nil)))
}