Using alternative contexts

README.md

@@ -32,6 +32,48 @@ func main() {
 }
 ```
 
+By default, `context.Background()` is used to generate contexts. If you need to provide an alternative method to support environments, like AppEngine, you can provide a RequestContextGenerator.
+
+```go
+package main
+
+import (
+  "net/http"
+
+  "golang.org/x/net/context"
+  "github.com/graphql-go/handler"
+  "google.golang.org/appengine"
+)
+
+type contextGenerator struct {
+
+}
+
+func (cg *contextGenerator) MakeContext(w http.ResponseWriter, r *http.Request) (context.Context, error) {
+    ctx := appengine.NewContext(r)
+
+    return ctx, nil
+}
+
+func main() {
+
+  // define GraphQL schema using relay library helpers
+  schema := graphql.NewSchema(...)
+
+  h := handler.New(&handler.Config{
+    Schema: schema,
+    Pretty: true,
+  })
+
+  cg := &contextGenerator{}
+  h.SetRequestContextGenerator(cg)
+
+  // serve HTTP
+  http.Handle("/graphql", h)
+  http.ListenAndServe(":8080", nil)
+}
+```
+
 ### Details
 
 The handler will accept requests with

handler.go

@@ -21,8 +21,10 @@ const (
 type Handler struct {
 	Schema *graphql.Schema
 
+	rcg RequestContextGenerator
 	pretty bool
 }
+
 type RequestOptions struct {
 	Query         string                 `json:"query" url:"query" schema:"query"`
 	Variables     map[string]interface{} `json:"variables" url:"variables" schema:"variables"`
@@ -143,9 +145,29 @@ func (h *Handler) ContextHandler(ctx context.Context, w http.ResponseWriter, r *
 	}
 }
 
+type RequestContextGenerator interface {
+	MakeContext(w http.ResponseWriter, r *http.Request) (context.Context, error)
+}
+
+func (h *Handler) SetRequestContextGenerator(rcg RequestContextGenerator) {
+	h.rcg = rcg
+}
+
+func (h *Handler) GetContext(w http.ResponseWriter, r *http.Request) (ctx context.Context, err error) {
+	if h.rcg != nil {
+		return h.rcg.MakeContext(w, r)
+	} else {
+		return context.Background(), nil
+	}
+}
+
 // ServeHTTP provides an entrypoint into executing graphQL queries.
 func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-	h.ContextHandler(context.Background(), w, r)
+	if ctx, err := h.GetContext(w, r); err != nil {
+		panic(err)
+	} else {
+		h.ContextHandler(ctx, w, r)
+	}
 }
 
 type Config struct {