Generally I would advise you pick Node.js for your backend if you want to run a GraphQL service. The main reason for this is the tooling and support you get from the language around GraphQL and the native feel due to the spec being initially written in JavaScrip for JavaScript. However that isn't to say that you couldn't use Go for a service underneath your GrahpQL layer - but I would say that's probably complicating it too much to begin with.
Node.js has great support for reading from databases and using a server such as Koa will give you great performance (we operate several Node.js services in Koa with over 1000req/s). Additionally it keeps your initial simple stack in the same language so it will be easier for you to jump backwards and forwards.
If you were not to use GraphQL then I'd say it's really up to you whether you want Go in your ecosystem or not. It's a fantastic language and super performant, along with being more memory efficient than Node (if you are worried about costs at large scale).
If you're at infancy stages and haven't picked certain parts - and this is a customer facing application - then I would recommend you look at Preact instead of React and URQL (instead of Apollo Client). Both are great libraries that are very performant and don't need much advanced learning. Additional swap out MySQL for PostgresSQL (they are interop primarily, but offers you more features as you grow) for its ACID compliance, better performance at scale and support for NoSQL if you were to go that way.
