The MarshalValue function returns an error if you try to marshal a value like var v any = nil, despite the same value marshaling correctly to BSON "null" when using Marshal.

Check out an example using MarshalValue here. Check out an example using Marshal here.

Definition of done:

• Calling bson.MarshalValue(nil) returns type "bsontype.Null", an encoded BSON "null" value, and no error.