Move websocket headers to opt function 'WithWebsocketHeaders' (#365)

Follow-up up on the discussion in
#360 (review).

Move websocket headers to and opt function 'WithWebsocketHeaders'.

Note this is a breaking change for users using the main branch
(but not for users on tagged releases).

I have:
- [x] Written a clear PR title and description (above)
- [x] Signed the [Khan Academy CLA](https://www.khanacademy.org/r/cla)
- [x] Added tests covering my changes, if applicable
- [x] Included a link to the issue fixed, if applicable
- [x] Included documentation, for new features
- [x] Added an entry to the changelog

graphql/client.go

@@ -133,16 +133,10 @@ type WebSocketOption func(*webSocketClient)
 //
 // The client does not support queries nor mutations, and will return an error
 // if passed a request that attempts one.
-func NewClientUsingWebSocket(endpoint string, wsDialer Dialer, headers http.Header, opts ...WebSocketOption) WebSocketClient {
-	if headers == nil {
-		headers = http.Header{}
-	}
-	if headers.Get("Sec-WebSocket-Protocol") == "" {
-		headers.Add("Sec-WebSocket-Protocol", "graphql-transport-ws")
-	}
+func NewClientUsingWebSocket(endpoint string, wsDialer Dialer, opts ...WebSocketOption) WebSocketClient {
 	client := &webSocketClient{
 		Dialer:        wsDialer,
-		Header:        headers,
+		header:        http.Header{},
 		errChan:       make(chan error),
 		endpoint:      endpoint,
 		subscriptions: subscriptionMap{map_: make(map[string]subscription)},
@@ -152,6 +146,10 @@ func NewClientUsingWebSocket(endpoint string, wsDialer Dialer, headers http.Head
 		opt(client)
 	}
 
+	if client.header.Get("Sec-WebSocket-Protocol") == "" {
+		client.header.Add("Sec-WebSocket-Protocol", "graphql-transport-ws")
+	}
+
 	return client
 }
 
@@ -163,6 +161,13 @@ func WithConnectionParams(connParams map[string]interface{}) WebSocketOption {
 	}
 }
 
+// WithWebsocketHeader sets a header to be sent to the server.
+func WithWebsocketHeader(header http.Header) WebSocketOption {
+	return func(ws *webSocketClient) {
+		ws.header = header
+	}
+}
+
 func newClient(endpoint string, httpClient Doer, method string) Client {
 	if httpClient == nil || httpClient == (*http.Client)(nil) {
 		httpClient = http.DefaultClient

graphql/websocket.go

@@ -45,7 +45,7 @@ const (
 
 type webSocketClient struct {
 	Dialer        Dialer
-	Header        http.Header
+	header        http.Header
 	endpoint      string
 	conn          WSConn
 	connParams    map[string]interface{}
@@ -169,7 +169,7 @@ func checkConnectionAckReceived(message []byte) (bool, error) {
 }
 
 func (w *webSocketClient) Start(ctx context.Context) (errChan chan error, err error) {
-	w.conn, err = w.Dialer.DialContext(ctx, w.endpoint, w.Header)
+	w.conn, err = w.Dialer.DialContext(ctx, w.endpoint, w.header)
 	if err != nil {
 		return nil, err
 	}

internal/integration/integration_test.go

@@ -164,13 +164,21 @@ func TestSubscriptionConnectionParams(t *testing.T) {
 		opts          []graphql.WebSocketOption
 	}{
 		{
-			name: "authorized_user_gets_counter",
+			name: "connection_params_authorized_user_gets_counter",
 			opts: []graphql.WebSocketOption{
 				graphql.WithConnectionParams(map[string]interface{}{
 					authKey: "authorized-user-token",
 				}),
 			},
 		},
+		{
+			name: "http_header_authorized_user_gets_counter",
+			opts: []graphql.WebSocketOption{
+				graphql.WithWebsocketHeader(http.Header{
+					authKey: []string{"authorized-user-token"},
+				}),
+			},
+		},
 		{
 			name:          "unauthorized_user_gets_error",
 			expectedError: "input: countAuthorized unauthorized\n",

internal/integration/roundtrip.go

@@ -167,7 +167,6 @@ func newRoundtripWebSocketClient(t *testing.T, endpoint string, opts ...graphql.
 		wsWrapped: graphql.NewClientUsingWebSocket(
 			endpoint,
 			&MyDialer{Dialer: dialer},
-			nil,
 			opts...,
 		),
 		t: t,

internal/integration/server/server.go

@@ -3,6 +3,7 @@ package server
 import (
 	"context"
 	"fmt"
+	"net/http"
 	"net/http/httptest"
 	"strconv"
 	"time"
@@ -198,6 +199,20 @@ func getAuthToken(ctx context.Context) string {
 	return ""
 }
 
+func authHeaderMiddleware(handler http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		ctx := r.Context()
+
+		token := r.Header.Get(AuthKey)
+		if token != "" {
+			ctx = withAuthToken(ctx, token)
+		}
+
+		r = r.WithContext(ctx)
+		handler.ServeHTTP(w, r)
+	})
+}
+
 func RunServer() *httptest.Server {
 	gqlgenServer := handler.New(NewExecutableSchema(Config{Resolvers: &resolver{}}))
 	gqlgenServer.AddTransport(transport.POST{})
@@ -216,7 +231,10 @@ func RunServer() *httptest.Server {
 		graphql.RegisterExtension(ctx, "foobar", "test")
 		return next(ctx)
 	})
-	return httptest.NewServer(gqlgenServer)
+
+	server := authHeaderMiddleware(gqlgenServer)
+
+	return httptest.NewServer(server)
 }
 
 type (