public GraphqlServiceBuilder enableWebSocket(boolean enableWebSocket) {
        this.enableWebSocket = enableWebSocket;
        return this;
    }
Enables <a href="https://github.com/enisdenjo/graphql-ws/blob/master/PROTOCOL.md">GraphQL over WebSocket Protocol</a>.
graphql/src/main/java/com/linecorp/armeria/server/graphql/GraphqlServiceBuilder.java