Just some background, and maybe a warning, on a service like Gogetdoc.com
They are a private company, not affiliated with the government or CDC. Basically what they are offering is a solution to employers and event organizers who would like to be able to verify vaccination status, but maintain a wall between themselves and the handling of personal information which may cause security and health information privacy concerns.
Basically they handle all of the personal information and issue a validated QR code to an individual, the employer need only scan the code with the software and reader provided by gogetdoc, and get a "good or not" response. In their model, an individual pays nothing for the service, the company needing the vax status pays. If an entity has not contracted with Gogetdoc, they can not read the code. I will concede that maybe Gogetdoc used some international standard and makes all data available for free to some central database...but that does not seem like a likely business model.
QR codes are not universal, or even necessarily contain any volume of information, they mainly supply a number or data string, that must then be referenced to a database. If you have a reader, but not access to the validation data, the code is worthless. This is why QR codes from the US for states like New York or Washington, do not work in Europe, or for that matter likely why New York's codes do not work in Washington. It is also why the EU as an entity set standards for each country to use in developing their own tracking systems, so a code from France would work in Italy, or any EU Country.
Long winded way to say that I would not count on a third party app like Gogetdoc working in any situation, unless the people wanting the code, told you to go to them to get one.