type Foo struct {
	ReadConcern *readconcern.ReadConcern
}

func main() {
	foo := &Foo{}

         _, err := bson.Marshal(foo)
	if err != nil {
		panic(err)
	}
}

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0x1195d78]goroutine 1 [running]:
go.mongodb.org/mongo-driver/mongo/readconcern.(*ReadConcern).MarshalBSONValue(0x3?)
        /Users/preston.vasquez/Developer/mongo-go-driver/mongo/readconcern/readconcern.go:73 +0x18
reflect.Value.call({0x11b7b40?, 0xc000014690?, 0x0?}, {0x11d831c, 0x4}, {0x0, 0x0, 0x121bce0?})
        /usr/local/go/src/reflect/value.go:586 +0xb07
reflect.Value.Call({0x11b7b40?, 0xc000014690?, 0x11b7b40?}, {0x0?, 0x11b7b40?, 0x1059b65?})
        /usr/local/go/src/reflect/value.go:370 +0xbc
go.mongodb.org/mongo-driver/bson/bsoncodec.DefaultValueEncoders.ValueMarshalerEncodeValue({}, {0xc0000061a0?, 0x50?}, {0x121b3f0, 0xc000036140}, {0x11b5f60?, 0xc000012048?, 0x11b5f60?})
        /Users/preston.vasquez/Developer/mongo-go-driver/bson/bsoncodec/default_value_encoders.go:557 +0x2d1
go.mongodb.org/mongo-driver/bson/bsoncodec.ValueEncoderFunc.EncodeValue(0xc000036140?, {0xc00011cc40?, 0xb?}, {0x121b3f0?, 0xc000036140?}, {0x11b5f60?, 0xc000012048?, 0xc00000d2e0?})
        /Users/preston.vasquez/Developer/mongo-go-driver/bson/bsoncodec/bsoncodec.go:178 +0x4a
go.mongodb.org/mongo-driver/bson/bsoncodec.(*StructCodec).EncodeValue(0x11a33a0?, {0xc00011cc40?, 0xc0?}, {0x121b3f0, 0xc000036140}, {0x11ba3c0?, 0xc000012048?, 0x500?})
        /Users/preston.vasquez/Developer/mongo-go-driver/bson/bsoncodec/struct_codec.go:181 +0x5f6
go.mongodb.org/mongo-driver/bson/bsoncodec.(*PointerCodec).EncodeValue(0xc00007a750, {0xc00011cc40?, 0xa0?}, {0x121b3f0, 0xc000036140}, {0x11a33a0?, 0xc000012048?, 0x107a4f9?})
        /Users/preston.vasquez/Developer/mongo-go-driver/bson/bsoncodec/pointer_codec.go:67 +0x53b
go.mongodb.org/mongo-driver/bson.(*Encoder).Encode(0xc00006e1e0, {0x11a33a0?, 0xc000012048})
        /Users/preston.vasquez/Developer/mongo-go-driver/bson/encoder.go:79 +0x174
go.mongodb.org/mongo-driver/bson.MarshalAppendWithContext({0xc00011cc40?, 0x48?}, {0x136ac80, 0x0, 0x0}, {0x11a33a0, 0xc000012048})
        /Users/preston.vasquez/Developer/mongo-go-driver/bson/marshal.go:103 +0x21d
go.mongodb.org/mongo-driver/bson.MarshalAppendWithRegistry(...)
        /Users/preston.vasquez/Developer/mongo-go-driver/bson/marshal.go:79
go.mongodb.org/mongo-driver/bson.MarshalWithRegistry(0xc0000061a0?, {0x11a33a0, 0xc000012048})
        /Users/preston.vasquez/Developer/mongo-go-driver/bson/marshal.go:65 +0x52
go.mongodb.org/mongo-driver/bson.Marshal(...)
        /Users/preston.vasquez/Developer/mongo-go-driver/bson/marshal.go:51
main.main()
        /Users/preston.vasquez/Developer/technical/workshop/mongo/bson/marshal-client-options/main.go:17 +0x45
exit status 2