I’m building my web framework in Go to make it feel more like the way NestJS handles JSON validation and sends HTTP error messages. Currently, I’m facing a challenge regarding how to determine if a field in a struct type is not provided. I don’t mean checking if the value is an empty string or a zero value, like using reflect.Value.IsZero() or reflect.Value.IsValid(). I want to know if there is a way to check if a struct has a field that is nil.

Example: 

type User struct{
    Name string `json:"name" validator:"optional"`
    Value string `json:"value" validator:"required"`
}
var data User
json.Unmarshal(body, &data) //name was not provided in the request so it should not be checked
errValidacao, hasError := validator.CheckPropretys[User](data)

func CheckProperties[T any](data T) (string, bool) {
    t := reflect.TypeOf(data)
    v := reflect.ValueOf(data)
    errorMessage := ""
    hasError := false

    if t.Kind() == reflect.Map {
        return "", hasError
    }

    for i := 0; i < t.NumField(); i++ {
        field := t.Field(i)
        value := v.Field(i)
        typeValidation := field.Tag.Get("validator")

        if typeValidation == "" {
            continue
        }

        toValidate := util.CommonToArray(typeValidation) // Returns an array with options to validate
        firstErr := true
        hasOptionalField := findOptional(toValidate)  
        
        if hasOptionalField && value.IsValid() && !value.IsZero() {
            continue
        }
        
        currentErrMessage := ""
        for j := 0; j < len(toValidate); j++ {
            test := string(testCase(toValidate[j], value, field))
            if firstErr && test != "" {
                currentErrMessage += test
                hasError = true
            } else if test != "" {
                currentErrMessage += "," + test
                hasError = true
            }
        }

        if errorMessage != "" && currentErrMessage != "" {
            errorMessage += ";"
            hasError = true
        }
        
        if currentErrMessage != "" {
            nameCamp := field.Tag.Get("json")
            if nameCamp == "" {
                nameCamp = field.Tag.Get("query")
            }
            errorMessage += nameCamp + ":" + currentErrMessage
            hasError = true
        }
    }
    return errorMessage, hasError
}

I have tried using every single function in the reflector package, i have not suceded, even json omitEmpty did not bring any results