Added MarshalJSON() method to MostListenedSong.

internal/radio/mostlistened.go

@@ -2,6 +2,7 @@ package radio
 
 import (
 	"bytes"
+	"encoding/json"
 	"errors"
 	"strconv"
 	"time"
@@ -21,6 +22,17 @@ func (mls *MostListenedSong) DateString() string {
 	return mls.Date.Format(MostListenedDateFormat)
 }
 
+func (mls *MostListenedSong) MarshalJSON() ([]byte, error) {
+	return json.Marshal(&struct {
+		Song      string `json:"song"`
+		Listeners int    `json:"listeners"`
+		Date      string `json:"date"`
+	}{
+		Song:      mls.Song,
+		Listeners: mls.Listeners,
+		Date:      mls.Date.UTC().Format(time.RFC3339)})
+}
+
 var mostListened MostListenedSong
 
 // CheckAndUpdateMostListenedSong compares current most played song with