added simple example, how to work with file upload

example.go

@@ -0,0 +1,121 @@
+package main
+
+import (
+	"fmt"
+	"github.com/graphql-go/graphql"
+	handler "github.com/jpascal/graphql-upload"
+	"net/http"
+	"os"
+	"path"
+)
+
+var UploadType = graphql.NewScalar(graphql.ScalarConfig{
+	Name:        "Upload",
+	Description: "Scalar upload object",
+})
+
+type FileWrapper struct {
+	File *os.File
+	Name string
+}
+
+var File = graphql.NewObject(graphql.ObjectConfig{
+	Name:        "File",
+	Description: "File object",
+	Fields: graphql.Fields{
+		"name": &graphql.Field{
+			Type: graphql.String,
+			Resolve: func(params graphql.ResolveParams) (interface{}, error) {
+				file := params.Source.(*FileWrapper)
+				name := path.Base(file.Name)
+				return name, nil
+			},
+		},
+		"url": &graphql.Field{
+			Type: graphql.String,
+			Resolve: func(params graphql.ResolveParams) (interface{}, error) {
+				file := params.Source.(*FileWrapper)
+				name := path.Base(file.File.Name())
+				return path.Join("/uploads/", name), nil
+			},
+		},
+		"size": &graphql.Field{
+			Type: graphql.Int,
+			Resolve: func(params graphql.ResolveParams) (interface{}, error) {
+				file := params.Source.(*FileWrapper)
+				if info, err := file.File.Stat(); err != nil {
+					return nil, err
+				} else {
+					return info.Size(), nil
+				}
+			},
+		},
+	},
+})
+
+func main() {
+	schema, err := graphql.NewSchema(
+		graphql.SchemaConfig{
+			Query: graphql.NewObject(
+				graphql.ObjectConfig{
+					Name: "Query",
+					Fields: graphql.Fields{
+						"file": &graphql.Field{
+							Type: File,
+							Args: graphql.FieldConfigArgument{
+								"id": &graphql.ArgumentConfig{
+									Type: graphql.NewNonNull(graphql.String),
+								},
+							},
+							Resolve: func(params graphql.ResolveParams) (interface{}, error) {
+								if fileId, ok := params.Args["id"].(string); ok {
+									file, _ := os.Open(fileId)
+									return &FileWrapper{File: file, Name: "some-file-name"}, nil
+								} else {
+									return nil, nil
+								}
+							},
+						},
+					},
+				}),
+			Mutation: graphql.NewObject(
+				graphql.ObjectConfig{
+					Name: "Mutation",
+					Fields: graphql.Fields{
+						"upload": &graphql.Field{
+							Type: graphql.String,
+							Args: graphql.FieldConfigArgument{
+								"file": &graphql.ArgumentConfig{
+									Type: UploadType,
+								},
+							},
+							Resolve: func(params graphql.ResolveParams) (interface{}, error) {
+								upload, uploadPresent := params.Args["file"].(handler.File)
+								if uploadPresent {
+									fmt.Print(upload.Filename)
+									// Store file somewhere...
+								}
+								return "file-id", nil
+							},
+						},
+					},
+				}),
+		})
+	if err != nil {
+		panic(err)
+	}
+
+	server := &http.Server{Addr: "0.0.0.0:5000", Handler: handler.New(func(request *handler.Request) interface{} {
+		return graphql.Do(graphql.Params{
+			RequestString:  request.Query,
+			OperationName:  request.OperationName,
+			VariableValues: request.Variables,
+			Schema:         schema,
+			Context:        request.Context,
+		})
+	}, &handler.Config{
+		MaxBodySize: 1024,
+	}),
+	}
+	server.ListenAndServe()
+}