Ability to distinguish between a supplied null value and a mising field

[threesquared]

Given a Struct like this:

type updateReq struct {
   Val      *string `json:"val" required:"false" nullable:"true" enum:"thing,thing1"`
   OtherVal *string `json:"otherval" required:"false" nullable:"true" pattern:"^[a-zA-Z0-9][a-zA-Z0-9.-]+[a-zA-Z0-9]$"`
}

If I send something like {"otherval":null} it passes validation as the values are not required and nullable but then my decoded input I just get {Val:<nil> OtherVal:<nil>} and it seems there is there is no way to work out if the value was omitted from the request or actually provided but as null

I want to be able to make this distinction in an update PATCH request so I know if the user wants to set the value to null or leave it as is.

[vearutop]

If I remember correctly (not near my laptop now to check), you need a double pointer (**string) for such resolution in encoding/json. Please try.