main.go

package main

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

	"github.com/graphql-go/graphql"
)

type Album struct {
	ID     string `json:"id,omitempty"`
	Artist string `json:"artist"`
	Title  string `json:"title"`
	Year   string `json:"year"`
	Genre  string `json:"genre"`
	Type   string `json:"type"`
}

type Artist struct {
	ID   string `json:"id,omitempty"`
	Name string `json:"name"`
	Type string `json:"type"`
}

type Song struct {
	ID       string `json:"id,omitempty"`
	Album    string `json:"album"`
	Title    string `json:"title"`
	Duration string `json:"duration"`
	Type     string `json:"type"`
}

var albums []Album = []Album{
	Album{
		ID:     "ts-fearless",
		Artist: "1",
		Title:  "Fearless",
		Year:   "2008",
		Type:   "album",
	},
}

var artists []Artist = []Artist{
	Artist{
		ID:   "1",
		Name: "Taylor Swift",
		Type: "artist",
	},
}

var songs []Song = []Song{
	Song{
		ID:       "1",
		Album:    "ts-fearless",
		Title:    "Fearless",
		Duration: "4:01",
		Type:     "song",
	},
	Song{
		ID:       "2",
		Album:    "ts-fearless",
		Title:    "Fifteen",
		Duration: "4:54",
		Type:     "song",
	},
}

func main() {

	songType := graphql.NewObject(graphql.ObjectConfig{
		Name: "Song",
		Fields: graphql.Fields{
			"id": &graphql.Field{
				Type: graphql.String,
			},
			"album": &graphql.Field{
				Type: graphql.String,
			},
			"title": &graphql.Field{
				Type: graphql.String,
			},
			"duration": &graphql.Field{
				Type: graphql.String,
			},
		},
	})

	artistType := graphql.NewObject(graphql.ObjectConfig{
	    Name: "Artist",
	    Fields: graphql.Fields{
	        "id": &graphql.Field{
	            Type: graphql.String,
	        },
	        "name": &graphql.Field{
	            Type: graphql.String,
	        },
	        "type": &graphql.Field{
	            Type: graphql.String,
	        },
	    },
	})


	albumType := graphql.NewObject(graphql.ObjectConfig{
	    Name: "Album",
	    Fields: graphql.Fields{
	        "id": &graphql.Field{
	            Type: graphql.String,
	        },
	        "artist": &graphql.Field{
	            Type: graphql.String,
	        },
	        "title": &graphql.Field{
	            Type: graphql.String,
	        },
	        "year": &graphql.Field{
	            Type: graphql.String,
	        },
	        "genre": &graphql.Field{
	            Type: graphql.String,
	        },
	        "type": &graphql.Field{
	            Type: graphql.String,
	        },
	    },
	})

	rootQuery := graphql.ObjectConfig(graphql.ObjectConfig{
		Name: "Query",
		Fields: graphql.Fields{
			"songs": &graphql.Field{
				Type: graphql.NewList(songType),
				Resolve: func(params graphql.ResolveParams) (interface{}, error) {
					return songs, nil
				},
			},
			"albums": &graphql.Field{
				Type: graphql.NewList(albumType),
				Resolve: func(params graphql.ResolveParams) (interface{}, error) {
					return albums, nil
				},
			},
			"artists": &graphql.Field{
				Type: graphql.NewList(artistType),
				Resolve: func(params graphql.ResolveParams) (interface{}, error) {
					return artists, nil
				},
			},
		},
	})

	schemaConfig := graphql.SchemaConfig{Query: graphql.NewObject(rootQuery)}
	schema, err := graphql.NewSchema(schemaConfig)
	if err != nil {
		log.Fatalf("failed to create new schema, error: %v", err)
	}

	http.HandleFunc("/graphql", func(w http.ResponseWriter, r *http.Request) {
		result := graphql.Do(graphql.Params{
			Schema:        schema,
			RequestString: r.URL.Query().Get("query"),
		})
		json.NewEncoder(w).Encode(result)
	})
	http.ListenAndServe(":12345", nil)
}