How to update in BD only the fields filled in my struct?

I have a struct to get the data from the user and update the info in the database. However, if the user lets a field in a blank, the correspondent field into DB will be blank. I don't want that, I would like to edit only the fields that the user informed.

My model:

type Business struct {
Id           uint64 `json:"id,omitempty"`
Company_name string `json:"company_name,omitempty"`
Trading_name string `json:"trading_name,omitempty"`
Facebook     string `json:"facebook,omitempty"`
Instagram    string `json:"instagram,omitempty"`
Tel          string `json:"tel,omitempty"`
User_id      uint64 `json:"user_id,omitempty"`
}

My controller:

func EditBusinessInfo(w http.ResponseWriter, r *http.Request) {
params := mux.Vars(r)
businessIDParams, err := strconv.ParseUint(params["businessID"], 10, 64)
if err != nil {
returns.ERROR(w, http.StatusBadRequest, err)
return
}
userIDInToken, err := auth.ExtractUserID(r)
if err != nil {
returns.ERROR(w, http.StatusInternalServerError, err)
return
}
db, err := db.ConnectToDB()
if err != nil {
returns.ERROR(w, http.StatusInternalServerError, err)
return
}
defer db.Close()
repository := repositories.NewUsersRepository(db)
businessInBD, err := repository.GetBusiness(businessIDParams)
if err != nil {
returns.ERROR(w, http.StatusInternalServerError, err)
return
}
if userIDInToken != businessInBD.User_id {
returns.ERROR(w, http.StatusUnauthorized, errors.New("você não pode editar a empresa de outra pessoa"))
return
}
if businessIDParams != businessInBD.Id {
returns.ERROR(w, http.StatusForbidden, errors.New("essa empresa não peertence a você"))
return
}
bodyRequest, err := ioutil.ReadAll(r.Body)
if err != nil {
returns.ERROR(w, http.StatusBadRequest, err)
return
}
var business models.Business
if err := json.Unmarshal(bodyRequest, &business); err != nil {
returns.ERROR(w, http.StatusUnprocessableEntity, err)
return
}
if err := repository.EditBusinessInfo(userIDInToken, business); err != nil {
returns.ERROR(w, http.StatusInternalServerError, err)
return
}
returns.JSON_RESPONSE(w, http.StatusOK, nil)
}

An int and string both have default values, so if you don't assign a value to them they will be populated with their default value (0 or ""). Since they will always have a value assigned, the omitempty tag will never come into play.

A common solution to this issue is to make your struct fields be pointers, if a pointer isn't set then it is nil. the nil value will then trigger the json marshaler to recognize the omitempty tag. And when you insert to you DB those values will be null/nil as well.

You should evaluate which fields need a value and which can be allowed to be empty in case your DB has integrity constraints. You will also have to add nil checks in your code when working with data.