Merge pull request #487 from ainilili/patch-1

Change the double quotation marks from simplified to English

README.md

@@ -57,7 +57,7 @@ func main() {
 		log.Fatalf("failed to execute graphql operation, errors: %+v", r.Errors)
 	}
 	rJSON, _ := json.Marshal(r)
-	fmt.Printf("%s \n", rJSON) // {“data”:{“hello”:”world”}}
+	fmt.Printf("%s \n", rJSON) // {"data":{"hello":"world"}}
 }
 ```
 For more complex examples, refer to the [examples/](https://github.com/graphql-go/graphql/tree/master/examples/) directory and [graphql_test.go](https://github.com/graphql-go/graphql/blob/master/graphql_test.go).