NewNullInt32 returns a null if i == 0, otherwise it returns the int32 which was input.

NewNullInt64 returns a null if i == 0, otherwise it returns the int64 which was input.

NewNullString returns a null if s is empty, otherwise it returns the string which was input.

NewNullTime returns a null if t is the zero value for time.Time, otherwise it returns the time which was input.

NewNullUUID returns a null if i == uuid.Nil, otherwise it returns the int32 which was input.