Golang, how to use a struct to write JSON response over HTTP? - http

Question

The Goal:
Using github.com/neelance/graphql-go starwars example, I'm trying to write a JSON response to my ReactJS client. That struct stuff is completely new for me, Golang as well btw.
The question:
What should data variable be in order to get the appropriate response to the following example GraphQL query?
query clientQuery {
character(id: 1000) {
name
appearsIn
}
}
Additional info:
From what I've read here and there, data must be some kind of struct. I've got plenty of structs available in the example (see starwars.go below).
The Code to be modified (main.go):
package main
import (
"encoding/json"
"log"
"net/http"
"github.com/neelance/graphql-go"
"github.com/neelance/graphql-go/example/starwars"
"github.com/neelance/graphql-go/relay"
)
var schema *graphql.Schema
func init() {
schema = graphql.MustParseSchema(starwars.Schema, &starwars.Resolver{})
}
func main() {
port := ":8080"
log.Printf(`GraphQL server starting up on http://localhost%v`, port)
http.Handle("/query", &relay.Handler{Schema: schema})
http.HandleFunc("/graphql", func(w http.ResponseWriter, r *http.Request) {
// THIS IS SUPER WRONG, data should be something
// like data := starwars.Resolver{} or so?
data := `{"data":{"character":{"name":"Luke Skywalker","appearsIn":["NEWHOPE","EMPIRE","JEDI"]}}}`
w.Header().Set("Content-Type", "application/json")
w.WriteHeader(http.StatusCreated)
json.NewEncoder(w).Encode(data)
})
log.Fatal(http.ListenAndServe(port, nil))
}
REFERENCE 1 - starwars.go
REFERENCE 2 - relay.go

Answer 1

You question is a bit confusing. You are asking about JSON, but your wanted response is not in a valid JSON format: It looks like you added unrelated GraphQL information.
I am not sure if this is an question about GraphQL or JSON. I will try to answer it anyway.
Your example data looks like this, therefore I assume that is the result you want to generate:
data := `{"data":{"character":{"name":"Luke Skywalker","appearsIn":["NEWHOPE","EMPIRE","JEDI"]}}}`
A clean way to make Go generate a proper JSON is to create Structs which contain the data:
type Response struct {
Data Data `json:"data"`
}
type Data struct {
Character Character `json:"characer"`
}
type Character struct {
Name string `json:"name"`
AppearsIn []string `json:"appearsIn"`
}
Then you can define the data like this:
data := Response{
Data: Data{
Character: Character{
Name: "Luke Skywalker",
AppearsIn: []string{"NEWHOPE", "EMPIRE", "JEDI"},
},
},
}
Perhaps this question isn't about JSON rather than GraphQL. In this case you need to clarify your question.
References
Details about JSON tags (ie json:".."): https://golang.org/pkg/encoding/json/#Marshal
Example with Structs: https://gobyexample.com/structs

Answer 2

Here is a simpler example, which would have helped me if it had been here.
type Password struct {
Password string `json:"password"`
}
func keyHandler(w http.ResponseWriter, r *http.Request) {
response := Password{"password"}
w.Header().Set("Content-Type", "application/json")
w.WriteHeader(http.StatusCreated)
json.NewEncoder(w).Encode(response)
}