Fix goroutine leak after close

It was possible for the Close() function to exit without all goroutines
existing. By closing these channels before the after function, all
goroutines are forced to exit before.

agent.go

@@ -109,8 +109,9 @@ type Agent struct {
 	extIPMapper *externalIPMapper
 
 	// State for closing
-	done chan struct{}
-	err  atomicError
+	done         chan struct{}
+	taskLoopDone chan struct{}
+	err          atomicError
 
 	gatherCandidateCancel func()
 
@@ -213,6 +214,7 @@ func (a *Agent) taskLoop() {
 		close(a.chanState)
 		close(a.chanCandidate)
 		close(a.chanCandidatePair)
+		close(a.taskLoopDone)
 	}()
 
 	for {
@@ -289,6 +291,7 @@ func NewAgent(config *AgentConfig) (*Agent, error) { //nolint:gocognit
 		onConnected:       make(chan struct{}),
 		buffer:            packetio.NewBuffer(),
 		done:              make(chan struct{}),
+		taskLoopDone:      make(chan struct{}),
 		startedCh:         startedCtx.Done(),
 		startedFn:         startedFn,
 		portmin:           config.PortMin,
@@ -421,12 +424,12 @@ func (a *Agent) startOnConnectionStateChangeRoutine() {
 					}
 					return
 				}
-				a.onConnectionStateChange(s)
+				go a.onConnectionStateChange(s)
 
 			case c, isOpen := <-a.chanCandidate:
 				if !isOpen {
 					for s := range a.chanState {
-						a.onConnectionStateChange(s)
+						go a.onConnectionStateChange(s)
 					}
 					return
 				}
@@ -897,20 +900,15 @@ func (a *Agent) Close() error {
 		return err
 	}
 
-	done := make(chan struct{})
-
 	a.afterRun(func(context.Context) {
 		a.gatherCandidateCancel()
-		close(done)
 	})
-
 	a.err.Store(ErrClosed)
 
 	a.removeUfragFromMux()
 
 	close(a.done)
-
-	<-done
+	<-a.taskLoopDone
 	return nil
 }