Let's actually hide RWMutex's methods to clean a namespace.

internal/radio/listener_counter.go

@@ -10,7 +10,7 @@ import (
 
 // ListenerCounter stores the current and peak numbers of listeners.
 type ListenerCounter struct {
-	sync.RWMutex
+	mutex         sync.RWMutex
 	current, peak int
 }
 
@@ -21,22 +21,22 @@ func NewListenerCounter() *ListenerCounter {
 
 // Current returns a number of current listeners.
 func (l *ListenerCounter) Current() int {
-	l.RLock()
-	defer l.RUnlock()
+	l.mutex.RLock()
+	defer l.mutex.RUnlock()
 	return l.current
 }
 
 // Current returns a number of peak listeners.
 func (l *ListenerCounter) Peak() int {
-	l.RLock()
-	defer l.RUnlock()
+	l.mutex.RLock()
+	defer l.mutex.RUnlock()
 	return l.peak
 }
 
 // Inc increments by 1 a current number of listeners and updates a peak number.
 func (l *ListenerCounter) Inc() int {
-	l.Lock()
-	defer l.Unlock()
+	l.mutex.Lock()
+	defer l.mutex.Unlock()
 	if l.current == math.MaxInt {
 		// We panic here because if this will ever happen, then something's going certainly wrong.
 		panic(fmt.Sprint("a current number of listeners exceeded MaxInt which is", math.MaxInt))
@@ -51,8 +51,8 @@ func (l *ListenerCounter) Inc() int {
 // Dec decrements by 1 a current number of listeners. An error will occur if
 // a resulting number is less than 0.
 func (l *ListenerCounter) Dec() (int, error) {
-	l.Lock()
-	defer l.Unlock()
+	l.mutex.Lock()
+	defer l.mutex.Unlock()
 	if l.current == 0 {
 		return l.current, errors.New("an attempt to decrement a number of current listeners down to less than 0")
 	}
@@ -61,8 +61,8 @@ func (l *ListenerCounter) Dec() (int, error) {
 }
 
 func (l *ListenerCounter) MarshalJSON() ([]byte, error) {
-	l.RLock()
-	defer l.RUnlock()
+	l.mutex.RLock()
+	defer l.mutex.RUnlock()
 	return json.Marshal(&struct {
 		Current int `json:"current"`
 		Peak    int `json:"peak"`

internal/radio/mostlistened.go

@@ -13,7 +13,7 @@ const MostListenedDateFormat string = "02 January 2006 at 15:04:05 MST"
 
 // MostListenedSong holds a metadata for a most listened song.
 type MostListenedSong struct {
-	sync.RWMutex
+	mutex     sync.RWMutex
 	Date      time.Time `json:"date"`
 	Listeners int       `json:"listeners"`
 	Song      string    `json:"song"`
@@ -21,8 +21,8 @@ type MostListenedSong struct {
 }
 
 func (mls *MostListenedSong) Update(song Song) {
-	mls.Lock()
-	defer mls.Unlock()
+	mls.mutex.Lock()
+	defer mls.mutex.Unlock()
 	if song.Artist == "" {
 		return
 	}
@@ -35,8 +35,8 @@ func (mls *MostListenedSong) Update(song Song) {
 }
 
 func (mls *MostListenedSong) Get() *MostListenedSong {
-	mls.RLock()
-	defer mls.RUnlock()
+	mls.mutex.RLock()
+	defer mls.mutex.RUnlock()
 
 	if mls.Date.Year() == 1 {
 		return nil
@@ -50,8 +50,8 @@ func (mls *MostListenedSong) Get() *MostListenedSong {
 
 // Load parses given data and fill a MostListenedSong.
 func (mls *MostListenedSong) Load(data []byte) (err error) {
-	mls.Lock()
-	defer mls.Unlock()
+	mls.mutex.Lock()
+	defer mls.mutex.Unlock()
 
 	lines := bytes.Split(data, []byte{'\n'})
 	if len(lines) != 3 {

internal/radio/playlist.go

@@ -10,7 +10,7 @@ import (
 
 // Playlist holds a list of paths to a song files.
 type Playlist struct {
-	sync.Mutex
+	mutex    sync.Mutex
 	filePath string
 	playlist []string
 	cur      int
@@ -27,8 +27,8 @@ func NewPlaylist(filePath string, repeat bool) (*Playlist, error) {
 // Next returns the next song to play. Returns an empty string if repeat is
 // false and the end of a playlist was reached.
 func (p *Playlist) Next() (song string) {
-	p.Lock()
-	defer p.Unlock()
+	p.mutex.Lock()
+	defer p.mutex.Unlock()
 	if p.cur == len(p.playlist) {
 		// If the end of a playlist was reached and repeat is set to true,
 		// then go back to the head of it, thus repeating it. Return an empty
@@ -55,10 +55,10 @@ func (p *Playlist) load() error {
 		return errors.New("a playlist file is empty. Did not update")
 	}
 
-	p.Lock()
+	p.mutex.Lock()
 	p.playlist = strings.Split(string(data), "\n")
 	p.cur = 0
-	p.Unlock()
+	p.mutex.Unlock()
 
 	return nil
 }

internal/radio/song.go

@@ -42,7 +42,7 @@ func (s *Song) MarshalJSON() ([]byte, error) {
 // SongList holds a currently playing song and a list of previously played ones
 // with a maximal length of maxLen.
 type SongList struct {
-	sync.RWMutex
+	mutex     sync.RWMutex
 	current   Song
 	lastSongs []Song
 	maxLen    int
@@ -55,8 +55,8 @@ func NewSongList(maxLen int) *SongList {
 
 // Add a new song that is currently playing and update a list.
 func (sl *SongList) Add(newSong Song) {
-	sl.Lock()
-	defer sl.Unlock()
+	sl.mutex.Lock()
+	defer sl.mutex.Unlock()
 
 	if sl.current.StartAt.Year() == 1 {
 		sl.current = newSong
@@ -73,8 +73,8 @@ func (sl *SongList) Add(newSong Song) {
 
 // Current returns a currently playing song or nil if it isn't set yet.
 func (sl *SongList) Current() *Song {
-	sl.RLock()
-	defer sl.RUnlock()
+	sl.mutex.RLock()
+	defer sl.mutex.RUnlock()
 	if sl.current.StartAt.Year() == 1 {
 		return nil
 	}
@@ -89,8 +89,8 @@ func (sl *SongList) Current() *Song {
 // UpdateCurrentMaxListeners checks and updates a maximal number of listeners
 // for a current song.
 func (sl *SongList) UpdateCurrentMaxListeners(listeners int) {
-	sl.Lock()
-	defer sl.Unlock()
+	sl.mutex.Lock()
+	defer sl.mutex.Unlock()
 	if listeners > sl.current.MaxListeners {
 		sl.current.MaxListeners = listeners
 	}
@@ -98,8 +98,8 @@ func (sl *SongList) UpdateCurrentMaxListeners(listeners int) {
 
 // List returns a list of lastly played songs.
 func (sl *SongList) List() []Song {
-	sl.RLock()
-	defer sl.RUnlock()
+	sl.mutex.RLock()
+	defer sl.mutex.RUnlock()
 	return sl.lastSongs
 }