Unable to use GraphiQL explorer on example

[riszkymf]

Steps to reproduce:

1. Run server.ts example
2. Open localhost:3000/graphql on browser.

Analysis
Looking at mod.ts line 57 it shows that graphiql options is enabled by default.

        this.server.post(
            "/graphql",
            async (ctx: any, next: any) => {
                const resp = await GraphQLHTTP<Request>({ schema, rootValue, context: (request) => ({ request }), graphiql: true })(ctx.req);
                ctx.res = resp;
                await next();
            },
        );

However the post function prevent user from accessing the GraphiQL explorer on browser.

Possible Solution

1. Use graphiql: true as an option argument, use get function if it's true.