how do i fix this type ‘Future<dynamic>’ is not a subtype of type ‘String’ The relevant error-causing widget was SavedTab

This is the widget tree returns this error

'Future' is not a subtype of type 'String' The relevant error-causing widget was SavedTab

  Widget build(BuildContext context) {
    return Container(
      child: Stack(
        children: [
          FutureBuilder<QuerySnapshot>(
            future: productsRef
                .document(_firebaseServices.getUserId())
                .collection("Saved")
                .getDocuments(),
            builder: (context, snapshot) {
              if (snapshot.hasError) {
                return Scaffold(
                  body: Center(
                    child: Text("Error: ${snapshot.error}"),
                  ),
                );
              }

              // Collection Data ready to display
              if (snapshot.connectionState == ConnectionState.done) {
                // Display the data inside a list view
                return ListView(
                  padding: EdgeInsets.only(
                    top: 108.0,
                    bottom: 12.0,
                  ),
                  children: snapshot.data.documents.map((document) {
                    return GestureDetector(
                      onTap: () {
                        Navigator.push(
                            context,
                            MaterialPageRoute(
                              builder: (context) => ProductPage(
                                productId: document.documentID,
                              ),
                            ));
                      },
                      child: FutureBuilder(
                        future: _firebaseServices.productsRef
                            .document(document.documentID)
                            .get(),
                        builder: (context, productSnap) {
                          if (productSnap.hasError) {
                            return Container(
                              child: Center(
                                child: Text("${productSnap.error}"),
                              ),
                            );
                          }

                          if (productSnap.connectionState ==
                              ConnectionState.done) {
                            Map _productMap = productSnap.data.data();
                          }
                        },
                      ),
                    );
                  }).toList(),
                );
              }

              // Loading State
              return Scaffold(
                body: Center(
                  child: CircularProgressIndicator(),
                ),
              );
            },
          ),
          CustomActionBar(
            title: "Saved",
            hasBackArrrow: false,
          ),
        ],
      ),
    );
  }
}

Read more here: https://stackoverflow.com/questions/65078496/how-do-i-fix-this-type-futuredynamic-is-not-a-subtype-of-type-string-the-r