Snapshot connected users under client lock

client.go

@@ -124,7 +124,14 @@ func (b *Barnard) OnConnect(e *gumble.ConnectEvent) {
 	b.UiTree.Rebuild()
 	b.Ui.Refresh()
 
-	for _, u := range b.Client.Users {
+	var users []*gumble.User
+	b.Client.Do(func() {
+		users = make([]*gumble.User, 0, len(b.Client.Users))
+		for _, u := range b.Client.Users {
+			users = append(users, u)
+		}
+	})
+	for _, u := range users {
 		b.UserConfig.UpdateUser(u)
 		b.rememberUserChannel(u)
 	}

fix.txt

@@ -272,7 +272,7 @@ Priority 3: configuration, UI, and binding hardening
     seconds for the protocol, creating a huge ban duration. Reject negative
     durations and validate mask/address before sending.
 
-36. Admin, tree, and client code read mutable maps outside Client.Do
+[x] 36. Admin, tree, and client code read mutable maps outside Client.Do
     Files: admin.go, ui_tree.go, client.go
     UI code ranges Client.Users, Channels, Channel.Users, and Children while
     network handlers mutate them. This overlaps issue 2 but must be fixed on