In ListenerCounter a sync.Mutex was replaced by a sync.RWMutex.

internal/radio/listener_counter.go

@@ -10,7 +10,7 @@ import (
 
 // ListenerCounter stores the current and peak numbers of listeners.
 type ListenerCounter struct {
-	sync.Mutex
+	sync.RWMutex
 	current, peak int
 }
 
@@ -21,15 +21,15 @@ func NewListenerCounter() *ListenerCounter {
 
 // Current returns a number of current listeners.
 func (l *ListenerCounter) Current() int {
-	l.Lock()
+	l.RLock()
-	defer l.Unlock()
+	defer l.RUnlock()
 	return l.current
 }
 
 // Current returns a number of peak listeners.
 func (l *ListenerCounter) Peak() int {
-	l.Lock()
+	l.RLock()
-	defer l.Unlock()
+	defer l.RUnlock()
 	return l.peak
 }
 
@@ -61,8 +61,8 @@ func (l *ListenerCounter) Dec() (int, error) {
 }
 
 func (l *ListenerCounter) MarshalJSON() ([]byte, error) {
-	l.Lock()
+	l.RLock()
-	defer l.Unlock()
+	defer l.RUnlock()
 	return json.Marshal(&struct {
 		Current int `json:"current"`
 		Peak    int `json:"peak"`