Graphql Subscriptions working with Gin have error

Question

I reference this code Graphql Subscriptions not working with Gin and I change r.POST("/query", graphqlHandler()) to r.Any("/query", graphqlHandler()),but I use postman always get "101 Switching Protocols" error like this picture
error picture

package main

import (
"github.com/gin-gonic/gin"
"github.com/jawil003/gqlgen-todos/graph"
"github.com/jawil003/gqlgen-todos/graph/generated"

    "github.com/99designs/gqlgen/graphql/handler"
    "github.com/99designs/gqlgen/graphql/playground"

)

// Defining the Graphql handler
func graphqlHandler() gin.HandlerFunc {
// 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(c *gin.Context) {
        h.ServeHTTP(c.Writer, c.Request)
    }

}

// Defining the Playground handler
func playgroundHandler() gin.HandlerFunc {
h := playground.Handler("GraphQL", "/query")

    return func(c *gin.Context) {
        h.ServeHTTP(c.Writer, c.Request)
    }

}

func main() {
// Setting up Gin
r := gin.Default()
r.POST("/query", graphqlHandler())
r.GET("/", playgroundHandler())
r.Run(":4000")
}

Is there any known solution to make gin work with graphql subscriptions? thx