You can find step by step guide for Golang Part 1 here And React Part 2 here to understand this demo properly.
for golang graphql gqlgen package is used. for reacjs applo-client is used.
cd golang
go get ./
go run main.go
cd reactjs
npm install
npm start
Golang graphql server will start on http://localhost:8888
React server will start on http://localhost:3000
Checkout full blog for Golang Part 1 here And React Part 2 here