The core bug was that they were reading from a map without checking if the map entry existed. Given a non-nil var m map[K]V, m[key] always succeeds (never panics). If the given entry doesn’t exist, it returns the zero value for the type, i.e. var v V. If V is a pointer type, accessing a field or method will panic (because the zero value is nil). If V is a struct or other value type, it can be used normally. That bug is on them. Any Go developer who isn’t a novice should know how maps and value types behave.