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: structlayout-svg.go
    path of file: ./repos/svgo/structlayout-svg
    
    the code of the file until where you have to start completion: // structlayout-svg: generate SVG struct layouts
package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"log"
	"os"

	"github.com/ajstarks/svgo"
	"honnef.co/go/tools/structlayout"
)

var title, bgcolor, scolor, pcolor string

func init() {
	flag.StringVar(&title, "t", "Structure Layout", "title")
	flag.StringVar(&bgcolor, "bgcolor", "rgb(240,240,240)", "background color")
	flag.StringVar(&scolor, "scolor", "steelblue", "structure color")
    
func main() {
	log.SetFlags(0)
	flag.Parse()

	// Decode the JSON
	var fields []structlayout.Field
	if err := json.NewDecoder(os.Stdin).Decode(&fields); err != nil {
		log.Fatal(err)
	}
	if len(fields) == 0 {
		return
	}

	// layout variables
	top := 50
	structheight := 50
	structwidth := 100
	gutter := 8
	byteheight := 10
	fontsize := byteheight + byteheight/2
	width := 600

	// Determine the height of the canvas
	height := top + gutter
	for _, f := range fields {
		height += byteheight * int(f.Size)
		height += gutter
	}
	x := width / 10
	y := top

	// Set up the canvas
	canvas := svg.New(os.Stdout)
	canvas.Start(width, height)
	canvas.Rect(0, 0, width, height, "fill:"+bgcolor)
	canvas.Gstyle(fmt.Sprintf("font-size:%dpx;font-family:sans-serif", fontsize))
	canvas.Text(x+structwidth/2, top/2, title, "text-anchor:middle;font-size:120%")

	// For every field, draw a labled box
	pos := int64(0)
	var fillcolor string
	nudge := (fontsize * 2) / 3
	for _, f := range fields {
		name := f.Name + " " + f.Type
		if f.IsPadding {
			name = "padding"
			fillcolor = pcolor
		} else {
			fillcolor = scolor
		}
		structheight = byteheight * int(f.Size)
		canvas.Rect(x, y, structwidth, structheight, "fill:"+fillcolor)
		canvas.Text(x+structwidth+10, y+nudge, fmt.Sprintf("%d", pos))
		canvas.Text(x+structwidth+fontsize*4, y+nudge, fmt.Sprintf("%s (size %d, align %d)", name, f.Size, f.Align))

		if f.Size > 2 {
			canvas.Text(x-10, y+structheight, fmt.Sprintf("%d", pos+f.Size-1), "text-anchor:end")
		}
		pos += f.Size
		y += structheight + gutter
	}
	canvas.Gend()
	canvas.End()
}