@required is just an annotation that allows analyzers let you know that you’re missing a named parameter and that’s it. so you can still compile the application and possibly get an exception if this named param was not passed.
However sound null-safety was added to dart, and required is now a keyword that needs to be passed to a named parameter so that it doesn’t let the compiler run if this parameter has not been passed. It makes your code more strict and safe.
If you truly think this variable can be null then you would change the type by adding a ? after it so that the required keyword is not needed, or you can add a default value to the parameter.