Solution for #84 learngo

todo.go

package main

import (
    "fmt"
    "io/ioutil"
    "strings"
    "log"
    "flag"
)

func main() {
    flag.Parse()
    var new_task string
    if len(flag.Args()) != 0 {
        new_task = strings.Join(flag.Args(), " ")
    }
    in, err := ioutil.ReadFile("todo.sample")
    if err != nil {
        log.Fatal("Couldn't open todo.sample", err)
    }
    line := strings.Split(string(in), "\n")
    if new_task != "" {
        line = append(line, new_task)
    }
    for i := 0; i < len(line); i++ {
        fmt.Printf("%d %s\n", i, line[i])
    }
    err = ioutil.WriteFile("todo.sample", []byte(strings.Join(line, "\n")), 0644)
    if err != nil {
        log.Fatal("Couldn't write todo.sample", err)
    }

}