Fetch site and check body length, with timing

// A solution to https://www.freelancer.com/projects/Google-Go/downloads-the-contents-com-Sees.html
package main

import (
	"container/list"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"time"
	"unicode/utf8"
)

// TimeEvent logs a time and an associated label.
type TimeEvent struct {
	Time  time.Time
	Label string
}

// MakeTime is a TimeEvent Factory, using the current time and a specified label.
func MakeTime(label string) TimeEvent {
	t := TimeEvent{
		Time:  time.Now(),
		Label: label,
	}
	return t
}

// Output a formatted table of total and inter-event timings, with labels.
func dumpLaps(l *list.List) {
	var item *list.Element = l.Front()

	var headTime = item.Value.(TimeEvent).Time
	var prevTime time.Time = item.Value.(TimeEvent).Time

	// Skip list head
	// item = item.Next()

	fmt.Printf("Time ms  Lap ms Event\n")
	for item != nil {
		value := item.Value.(TimeEvent)
		fmt.Printf("%5.0fms %5.0fms %s\n", value.Time.Sub(headTime).Seconds()*1000,
			value.Time.Sub(prevTime).Seconds()*1000, value.Label)
		prevTime = value.Time
		item = item.Next()
	}
}

// Compute the time difference in seconds between the first and last TimeEvent in a list.
func totalTime(l *list.List) float64 {
	var t0, t1 time.Time

	t0 = l.Front().Value.(TimeEvent).Time
	t1 = l.Back().Value.(TimeEvent).Time
	ret := t1.Sub(t0).Seconds()
	return ret
}

// Measure the length of the body of a given URL and the time taken to fetch it.
func main() {
	if len(os.Args) != 2 {
		log.Fatalf("Syntax: oo <absolute url>, like oo http://example.com\n")
	}

	url := os.Args[1]
	laps := list.New()

	laps.PushBack(MakeTime("Start"))
	resp, err := http.Get(url)
	if err != nil {
		log.Fatalf("Fatal error loading site: %+v\n", err)
	}
	defer resp.Body.Close()

	laps.PushBack(MakeTime("GET"))
	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		log.Fatalf("Fatal error reading body: %+v\n", err)
	}
	laps.PushBack(MakeTime("Read"))

	fmt.Printf("Body %d runes, %d bytes, %d bytes/sec.\n\n", len(body), utf8.RuneCount(body),
		int(float64(len(body))/totalTime(laps)))
	dumpLaps(laps)
}