You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: main.go
    path of file: ./repos/juju/scripts/juju-leasediff
    
    the code of the file until where you have to start completion: // Copyright 2021 Canonical Ltd.
// Licensed under the AGPLv3, see LICENCE file for details.

package main

import (
	"flag"
	"fmt"
	"log"
	"os"
	"strings"

	"github.com/juju/collections/set"
	"gopkg.in/yaml.v3"
)

func main() {
	flag.Parse()

	files := flag.Args()
	if len(files) == 0 {
		log.Fatal("expected at least on file")
	}

	reports := make([]Controller, len(files))
	for i, file := range files {
		f, err := os.Open(file)
		if err != nil {
			log.Fatal(err)
		}

		var report Controller
		if err := yaml.NewDecoder(f).Decode(&report); err != nil {
			log.Fatal(err)
		}

		reports[i] = report
	}

	// Process them to ensure that all leases are correctly held.
	sets := make([]set.Strings, len(reports))
	for i, report := range reports {
		set := set.NewStrings()
		for k, v := range report.Controller
    
func main() {
	flag.Parse()

	files := flag.Args()
	if len(files) == 0 {
		log.Fatal("expected at least on file")
	}

	reports := make([]Controller, len(files))
	for i, file := range files {
		f, err := os.Open(file)
		if err != nil {
			log.Fatal(err)
		}

		var report Controller
		if err := yaml.NewDecoder(f).Decode(&report); err != nil {
			log.Fatal(err)
		}

		reports[i] = report
	}

	// Process them to ensure that all leases are correctly held.
	sets := make([]set.Strings, len(reports))
	for i, report := range reports {
		set := set.NewStrings()
		for k, v := range report.ControllerLeases {
			set.Add(fmt.Sprintf("%s:%s", k, v.Holder))
		}
		for k, v := range report.ModelLeases {
			for app, lease := range v {
				set.Add(fmt.Sprintf("%s:%s:%s", k, app, lease.Holder))
			}
		}
		sets[i] = set
	}

	for i := 1; i < len(sets); i++ {
		a := sets[i-1]
		b := sets[i]

		x := a.Difference(b)
		y := b.Difference(a)

		if len(x) > 0 || len(y) > 0 {
			fmt.Println("Difference located:")
			fmt.Println(x)
			fmt.Println(y)
			return
		}

		for _, v0 := range a.SortedValues() {
			parts := strings.Split(v0, ":")
			if len(parts) == 2 {
				l0 := reports[i-1].ControllerLeases[parts[0]]
				l1 := reports[i].ControllerLeases[parts[0]]
				if l0.LeaseExpires != l1.LeaseExpires {
					fmt.Printf("Controller lease (%d - %d): %s:: %s - %s\n", i-1, i, parts[0], l0, l1)
				}
			} else if len(parts) == 3 {
				l0 := reports[i-1].ModelLeases[parts[0]][parts[1]]
				l1 := reports[i].ModelLeases[parts[0]][parts[1]]
				if l0.LeaseExpires != l1.LeaseExpires {
					fmt.Printf("Model lease (%d - %d): %s:: %s - %s\n", i-1, i, parts[0], l0, l1)
				}
			}
		}
	}
}