[test] fix unit test (#298)

# Description

fix random ci test failed

```
panic: send on closed channel

goroutine 422 [running]:
github.com/dogechain-lab/dogechain/protocol.(*syncPeerClient).handleStatusUpdate(0xc000160cf0, {0xfb7720, 0xc0025efc80}, {0xc000b6ca80, 0xc000bdf701})
	/home/runner/work/dogechain/dogechain/protocol/client.go:225 +0x3ec
```

# Changes include

- [x] Bugfix (non-breaking change that solves an issue)

# Testing

- [x] I have tested this code with the official test suite

protocol/client_test.go

@@ -352,9 +352,14 @@ func TestPeerConnectionUpdateEventCh(t *testing.T) {
 
 	go func() {
 		defer wgForConnectingStatus.Done()
+		wgForGossip.Wait()
 
 		for status := range client.GetPeerStatusUpdateCh() {
 			newStatuses = append(newStatuses, status)
+
+			if len(newStatuses) > 0 {
+				break
+			}
 		}
 	}()
 
@@ -377,9 +382,6 @@ func TestPeerConnectionUpdateEventCh(t *testing.T) {
 	// wait until 2 messages are propagated
 	wgForGossip.Wait()
 
-	// close to terminate goroutine
-	close(client.peerStatusUpdateCh)
-
 	// wait until collecting routine is done
 	wgForConnectingStatus.Wait()