###gqlgenとhttprouteの組み方
import (
     "net/http"
     ...
     "github.com/99designs/gqlgen/graphql/handler"
     "github.com/99designs/gqlgen/graphql/playground"
     "github.com/julienschmidt/httprouter"
)

// Defining the Playground handler
func PlaygroundHandler() httprouter.Handle {
	h := playground.Handler("GraphQL", "/query")

	return func(w http.ResponseWriter, req *http.Request, ps httprouter.Params) {
		h.ServeHTTP(w, req)
	}
}

// Defining the Graphql handler
func GraphqlHandler() httprouter.Handle {
      // NewExecutableSchema and Config are in the generated.go file
     // Resolver is in the resolver.go file
	h := handler.NewDefaultServer(generated.NewExecutableSchema(generated.Config{Resolvers: &graph.Resolver{}}))

	return func(w http.ResponseWriter, req *http.Request, ps httprouter.Params) {
		h.ServeHTTP(w, req)
	}
}

func main() {
	// Setting up httprouter
	r := httprouter.New()
	r.POST("/query", GraphqlHandler())
	r.GET("/", PlaygroundHandler())
	...
}