Refactor: move time out of gupta.GuptaReport.MarshalJSON

This is actually better as a field in the Report. This makes
testing easier and also belongs as a property to the report.

cmd/main.go

@@ -54,7 +54,7 @@ func main() {
 	defer m.Close()
 
 	for true {
-		report := gupta.GuptaReport{}
+		report := gupta.GuptaReport{Time: time.Now()}
 		line := readProcStatLine(r)
 		time.Sleep(time.Duration(interval) * time.Second)
 		if cpu {

gupta.go

@@ -15,6 +15,7 @@ func Hello() string {
 }
 
 type GuptaReport struct {
+	Time        time.Time
 	LoadAvarage float64
 	CPUUsage    *CPUStat `json:"cpu usage, omitempty"`
 	MemoryUsage *Memory  `json:"memory,omitempty"`
@@ -23,9 +24,8 @@ type GuptaReport struct {
 // usually you'd want a g GuptaReport reciever here ...
 // but than you could now check for the object properties ...
 func (g *GuptaReport) MarshalJSON() ([]byte, error) {
-	t := time.Now()
 	report := []byte(fmt.Sprintf("{\"timestamp\": \"%d\", \"metrics\": [",
-		t.Unix()))
+		g.Time.Unix()))
 	if g.CPUUsage != nil {
 		usage, _ := json.Marshal(g.CPUUsage)
 		report = append(report, usage...)