Unprocessed Entity error using Go fiber and mongodb

I have created a post Api in go giber to to create a prompt. From the frontend I am passing the payload creator which has a string type but in my prompt_model i have it as prmitive.ObjectId type.
when I am running the function c.BodyParser(&prompt) it throws the error bad request Unprocessable Entity.

Here is the Prompt model:

type Prompts struct{
	Id primitive.ObjectID `json:"id,omitempty" bson:"_id,omitempty"`
	Creator primitive.ObjectID `json:"creator,omitempty" bson:"creator,omitempty"`
	CreatorUser User `json:"creatorUser,omitempty" bson:"-"`
	Prompt string `json:"prompt,omitempty" validate:"required"`
	Tag string `json:"tag,omitempty" validate:"required"`

here is the code for create-prompt controller:

func CreatePrompt(c *fiber.Ctx) error {
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	var prompt models.Prompts

	// Extract session ID from the URL parameter
	// sessionID := c.FormValue("creator")
	// sessionObjectID, _ := primitive.ObjectIDFromHex(sessionID)
	// fmt.Printf("ss %v \n ",sessionID)

	// Validate the request body
	fmt.Println("dd", c.BodyParser(&prompt))
	if err := c.BodyParser(&prompt); err != nil {
		return c.Status(http.StatusBadRequest).JSON(responses.UserResponse{
			Status:  http.StatusBadRequest,
			Message: "error",
			Data:    &fiber.Map{"data": err.Error()},

	// Assuming the session ID is stored in the Creator field
	newPrompt := models.Prompts{
		Id:          primitive.NewObjectID(),
		Creator:     prompt.Creator,
		Prompt:      prompt.Prompt,
		Tag:         prompt.Tag,

	result, err := promptCollection.InsertOne(ctx, newPrompt)
	if err != nil {
		return c.Status(http.StatusInternalServerError).JSON(responses.UserResponse{
			Status:  http.StatusInternalServerError,
			Message: "error",
			Data:    &fiber.Map{"data": err.Error()},

	return c.Status(http.StatusCreated).JSON(responses.UserResponse{
		Status:  http.StatusCreated,
		Message: "success",
		Data:    &fiber.Map{"data": result},

here is the api call from frontend:

const response = await fetch("http://localhost:8000/create-prompt", {
        method: "POST",
        body: JSON.stringify({
          creator: session?.user.id,
          prompt: post.prompt,
          tag: post.tag,

here is the log for the payload data:


I tried to convert the creator from string type to objectId type before using the bodyParser method but it was in vein
what I am doing wrong exactly?