A simple timer to use for logging time between actions

timer.go

package timer

import (
	"log"
	"os"
	"time"
)

type TimeLogger interface {
	Printf(format string, v ...interface{})
}

type Timer struct {
	start   time.Time
	logger  TimeLogger
	message string
	active  bool
}

func (t *Timer) Start() {
	if t.active {
		t.start = time.Now()
	}
}

func (t *Timer) Stop() *Timer {
	if t.active {
		t.logger.Printf("%s in %.03f seconds", t.message, time.Since(t.start).Seconds())
	}
	return t
}

func (t *Timer) Restart(message string) {
	if t.active {
		t.start = time.Now()
		t.message = message
	}
}

func (t *Timer) StopAndRestart(message string) {
	if t.active {
		t.Stop()
		t.start = time.Now()
		t.message = message
	}
}

func NewTimer(message string, active bool, logger ...TimeLogger) Timer {
	if !active {
		return Timer{active: active}
	}
	if logger[0] == nil {
		logger[0] = log.New(os.Stdout, "Timer: ", log.LstdFlags)
	}
	return Timer{start: time.Now(), message: message, logger: logger[0], active: active}
}