diff --git a/lib/util/errors/merror.go b/lib/util/errors/merror.go
index 2ef7bc75..31a53aef 100644
--- a/lib/util/errors/merror.go
+++ b/lib/util/errors/merror.go
@@ -64,7 +64,7 @@ func (e *MError) Error() string {
 func (e *MError) Is(s error) bool {
 	is := errors.Is(e.cerr, s)
 	for _, e := range e.uerr {
-		is  = is || errors.Is(e, s)
+		is = is || errors.Is(e, s)
 		if is {
 			break
 		}
@@ -78,6 +78,14 @@ func (e *MError) Cause() []error {
 
 // Collect is used to collect multiple errors. `Unwrap` is noop and `Is(err, ErrMine) == true`. While `As(err, underlyingError)` do not work, you can still get underlying errors by `MError.Cause`.
 func Collect(cerr error, uerr ...error) error {
+	n := 0
+	for _, e := range uerr {
+		if e != nil {
+			uerr[n] = e
+			n++
+		}
+	}
+	uerr = uerr[:n]
 	if len(uerr) == 0 {
 		return nil
 	}
diff --git a/lib/util/errors/merror_test.go b/lib/util/errors/merror_test.go
index 37664123..d6c5576f 100644
--- a/lib/util/errors/merror_test.go
+++ b/lib/util/errors/merror_test.go
@@ -32,4 +32,8 @@ func TestCollect(t *testing.T) {
 	require.ErrorIsf(t, e, e1, "but errors.Is works for all errors")
 	require.Equal(t, e.(*serr.MError).Cause(), []error{e2, e3}, "get underlying errors")
 	require.NoError(t, serr.Collect(e3), "nil if there is no underlying error")
+
+	e4 := serr.Collect(e1, e2, nil).(*serr.MError)
+	require.Len(t, e4.Cause(), 1, "collect non-nil erros only")
+	require.NoError(t, serr.Collect(e3, nil, nil), "nil if all errors are nil")
 }
diff --git a/pkg/proxy/client/client_conn.go b/pkg/proxy/client/client_conn.go
index ee873c12..3eac1a5d 100644
--- a/pkg/proxy/client/client_conn.go
+++ b/pkg/proxy/client/client_conn.go
@@ -109,12 +109,5 @@ func (cc *ClientConnection) processMsg(ctx context.Context) error {
 }
 
 func (cc *ClientConnection) Close() error {
-	var errs []error
-	if err := cc.pkt.Close(); err != nil {
-		errs = append(errs, err)
-	}
-	if err := cc.connMgr.Close(); err != nil {
-		errs = append(errs, err)
-	}
-	return errors.Collect(ErrCloseConn, errs...)
+	return errors.Collect(ErrCloseConn, cc.pkt.Close(), cc.connMgr.Close())
 }
diff --git a/pkg/proxy/proxy.go b/pkg/proxy/proxy.go
index 93d22cbb..7f90bad8 100644
--- a/pkg/proxy/proxy.go
+++ b/pkg/proxy/proxy.go
@@ -158,11 +158,9 @@ func (s *SQLServer) onConn(ctx context.Context, conn net.Conn) {
 
 // Close closes the server.
 func (s *SQLServer) Close() error {
-	var errs []error
+	errs := make([]error, 0, 4)
 	if s.listener != nil {
-		if err := s.listener.Close(); err != nil {
-			errs = append(errs, err)
-		}
+		errs = append(errs, s.listener.Close())
 	}
 
 	s.mu.Lock()
diff --git a/pkg/server/server.go b/pkg/server/server.go
index 416fbdc2..b66bbf27 100644
--- a/pkg/server/server.go
+++ b/pkg/server/server.go
@@ -205,26 +205,18 @@ func (s *Server) Run(ctx context.Context) {
 }
 
 func (s *Server) Close() error {
-	var errs []error
+	errs := make([]error, 0, 4)
 	if s.Proxy != nil {
-		if err := s.Proxy.Close(); err != nil {
-			errs = append(errs, err)
-		}
+		errs = append(errs, s.Proxy.Close())
 	}
 	if s.NamespaceManager != nil {
-		if err := s.NamespaceManager.Close(); err != nil {
-			errs = append(errs, err)
-		}
+		errs = append(errs, s.NamespaceManager.Close())
 	}
 	if s.ConfigManager != nil {
-		if err := s.ConfigManager.Close(); err != nil {
-			errs = append(errs, err)
-		}
+		errs = append(errs, s.ConfigManager.Close())
 	}
 	if s.ObserverClient != nil {
-		if err := s.ObserverClient.Close(); err != nil {
-			errs = append(errs, err)
-		}
+		errs = append(errs, s.ObserverClient.Close())
 	}
 	if s.Etcd != nil {
 		var wg waitgroup.WaitGroup