Example of creating custom `graphql-go/handler` using `handler.NewRequestOptions()` to parse http.Requests

main.go

package main

import (
	"encoding/json"
	"net/http"

	"github.com/graphql-go/graphql"
	"github.com/graphql-go/handler"
	"github.com/graphql-go/relay/examples/starwars"
)

func myCustomGraphQLHandler(schema *graphql.Schema) func(http.ResponseWriter, *http.Request) {

	if schema == nil {
		// panic at time of initial execution
		panic("Graphql schema cannot be nil")
	}

	return func(rw http.ResponseWriter, r *http.Request) {

		// parse http.Request into handler.RequestOptions
		opts := handler.NewRequestOptions(r)

		// inject context objects http.ResponseWrite and *http.Request into rootValue
		// there is an alternative example of using `net/context` to store context instead of using rootValue
		rootValue := map[string]interface{}{
			"response": rw,
			"request":  r,
			"viewer":   "john_doe",
		}

		// execute graphql query
		// here, we passed in Query, Variables and OperationName extracted from http.Request
		params := graphql.Params{
			Schema:         *schema,
			RequestString:  opts.Query,
			VariableValues: opts.Variables,
			OperationName:  opts.OperationName,
			RootObject:     rootValue,
		}
		result := graphql.Do(params)


		// one way to render JSON without use of external libraries
		// alternatively, you can use libraries like `unrolled/render`
		js, err := json.Marshal(result)
		if err != nil {
			http.Error(rw, err.Error(), http.StatusInternalServerError)
			return
		}
		rw.Header().Set("Content-Type", "application/json")
		rw.Write(js)
	}

}

func main() {
	http.HandleFunc("/graphql/", myCustomGraphQLHandler(&starwars.Schema))
	http.ListenAndServe(":3000", nil)
}