Subscriptions

package main

import (
	"log"
	"net/http"
	"os"

	"github.com/99designs/gqlgen/graphql/handler"
	"github.com/99designs/gqlgen/graphql/handler/transport"
	"github.com/99designs/gqlgen/graphql/playground"
	"github.com/example/test/graph"
	"github.com/example/test/graph/generated"
)

const defaultPort = "8080"

func main() {
	port := os.Getenv("PORT")
	if port == "" {
		port = defaultPort
	}

	srv := handler.NewDefaultServer(generated.NewExecutableSchema(generated.Config{Resolvers: &graph.Resolver{}}))

	srv.AddTransport(&transport.Websocket{}) // <---- This is the important part!

	http.Handle("/", playground.Handler("GraphQL playground", "/query"))
	http.Handle("/query", srv)

	log.Printf("connect to http://localhost:%s/ for GraphQL playground", port)
	log.Fatal(http.ListenAndServe(":"+port, nil))
}

"""
Make sure you have at least something in your `Query` type.
If you don't have a query the playground will be unable
to introspect your schema!
"""
type Query {
  placeholder: String
}

"""
`Time` is a simple type only containing the current time as
a unix epoch timestamp and a string timestamp.
"""
type Time {
  unixTime: Int!
  timeStamp: String!
}

"""
`Subscription` is where all the subscriptions your clients can
request. You can use Schema Directives like normal to restrict
access.
"""
type Subscription {
  """
  `currentTime` will return a stream of `Time` objects.
  """
  currentTime: Time!
}

// CurrentTime is the resolver for the currentTime field.
func (r *subscriptionResolver) CurrentTime(ctx context.Context) (<-chan *model.Time, error) {
	// First you'll need to `make()` your channel. Use your type here!
	ch := make(chan *model.Time)

	// You can (and probably should) handle your channels in a central place outside of `schema.resolvers.go`.
	// For this example we'll simply use a Goroutine with a simple loop.
	go func() {
		// Handle deregistration of the channel here. Note the `defer`
		defer close(ch)

		for {
			// In our example we'll send the current time every second.
			time.Sleep(1 * time.Second)
			fmt.Println("Tick")

			// Prepare your object.
			currentTime := time.Now()
			t := &model.Time{
				UnixTime:  int(currentTime.Unix()),
				TimeStamp: currentTime.Format(time.RFC3339),
			}

			// The subscription may have got closed due to the client disconnecting.
			// Hence we do send in a select block with a check for context cancellation.
			// This avoids goroutine getting blocked forever or panicking,
			select {
			case <-ctx.Done(): // This runs when context gets cancelled. Subscription closes.
				fmt.Println("Subscription Closed")
				// Handle deregistration of the channel here. `close(ch)`
				return // Remember to return to end the routine.
			
			case ch <- t: // This is the actual send.
				// Our message went through, do nothing	
			}
		}
	}()

	// We return the channel and no error.
	return ch, nil
}

subscription {
  currentTime {
    unixTime
    timeStamp
  }
}

srv := handler.New(generated.NewExecutableSchema(generated.Config{Resolvers: &graph.Resolver{}}))
srv.AddTransport(transport.SSE{}) // <---- This is the important

// default server
srv.AddTransport(transport.Options{})
srv.AddTransport(transport.GET{})
srv.AddTransport(transport.POST{})
srv.AddTransport(transport.MultipartForm{})
srv.SetQueryCache(lru.New(1000))
srv.Use(extension.Introspection{})
srv.Use(extension.AutomaticPersistedQuery{
	Cache: lru.New(100),
})

curl -N --request POST --url http://localhost:8080/query \
--data '{"query":"subscription { currentTime { unixTime timeStamp } }"}' \
-H "accept: text/event-stream" -H 'content-type: application/json' \
--verbose

package main

import (
	"log"
	"net/http"
	"os"

	"github.com/99designs/gqlgen/graphql/handler"
	"github.com/99designs/gqlgen/graphql/handler/transport"
	"github.com/99designs/gqlgen/graphql/playground"
	"github.com/example/test/graph"
	"github.com/example/test/graph/generated"
)

const defaultPort = "8080"

func main() {
	port := os.Getenv("PORT")
	if port == "" {
		port = defaultPort
	}

	srv := handler.NewDefaultServer(generated.NewExecutableSchema(generated.Config{Resolvers: &graph.Resolver{}}))

	srv.AddTransport(&transport.Websocket{})

	http.Handle("/", playground.Handler("GraphQL playground", "/query"))
	http.Handle("/query", srv)

	log.Printf("connect to http://localhost:%s/ for GraphQL playground", port)
	log.Fatal(http.ListenAndServe(":"+port, nil))
}

type Query {
  placeholder: String
}

type Time {
  unixTime: Int!
  timeStamp: String!
}

type Subscription {
  currentTime: Time!
}

package graph

// This file will be automatically regenerated based on the schema, any resolver implementations
// will be copied through when generating and any unknown code will be moved to the end.

import (
	"context"
	"fmt"
	"time"

	"github.com/example/test/graph/generated"
	"github.com/example/test/graph/model"
)

// Placeholder is the resolver for the placeholder field.
func (r *queryResolver) Placeholder(ctx context.Context) (*string, error) {
	str := "Hello World"
	return &str, nil
}

// CurrentTime is the resolver for the currentTime field.
func (r *subscriptionResolver) CurrentTime(ctx context.Context) (<-chan *model.Time, error) {
	ch := make(chan *model.Time)

	go func() {
		defer close(ch)

		for {
			time.Sleep(1 * time.Second)
			fmt.Println("Tick")

			currentTime := time.Now()

			t := &model.Time{
				UnixTime:  int(currentTime.Unix()),
				TimeStamp: currentTime.Format(time.RFC3339),
			}

			select {
			case <-ctx.Done():
				// Exit on cancellation 
				fmt.Println("Subscription closed.")
				return
			
			case ch <- t:
				// Our message went through, do nothing
			}

		}
	}()
	return ch, nil
}

// Query returns generated.QueryResolver implementation.
func (r *Resolver) Query() generated.QueryResolver { return &queryResolver{r} }

// Subscription returns generated.SubscriptionResolver implementation.
func (r *Resolver) Subscription() generated.SubscriptionResolver { return &subscriptionResolver{r} }

type queryResolver struct{ *Resolver }
type subscriptionResolver struct{ *Resolver }