Disable IOReaderFactory for streaming requests (grpc-ecosystem#896)

An IOReaderFactory was being used to wrap request body for client/bidi streaming
requests.  This was causing the requests to be fully buffered before being sent
to the grpc server, thereby breaking streaming.  This commit changes that to
directly use request body.

Fixes grpc-ecosystem#894

Author: happyalu

examples/proto/examplepb/flow_combination.pb.gw.go

@@ -236,11 +236,7 @@ func request_{{.Method.Service.GetName}}_{{.Method.GetName}}_{{.Index}}(ctx cont
 		grpclog.Infof("Failed to start streaming: %v", err)
 		return nil, metadata, err
 	}
-	newReader, berr := utilities.IOReaderFactory(req.Body)
-	if berr != nil {
-		return nil, metadata, status.Errorf(codes.InvalidArgument, "%v", berr)
-	}
-	dec := marshaler.NewDecoder(newReader())
+	dec := marshaler.NewDecoder(req.Body)
 	for {
 		var protoReq {{.Method.RequestType.GoType .Method.Service.File.GoPkg.Path}}
 		err = dec.Decode(&protoReq)
@@ -303,8 +299,8 @@ var (
 				return nil, metadata, status.Errorf(codes.InvalidArgument, "%v", err)
 			} else {
 				protoReq.{{.FieldMaskField}} = fieldMask
-			}		
-	} {{end}}		
+			}
+	} {{end}}
 	{{end}}
 {{end}}
 {{if .PathParams}}
@@ -378,11 +374,7 @@ var (
 		grpclog.Infof("Failed to start streaming: %v", err)
 		return nil, metadata, err
 	}
-	newReader, berr := utilities.IOReaderFactory(req.Body)
-	if berr != nil {
-		return nil, metadata, berr
-	}
-	dec := marshaler.NewDecoder(newReader())
+	dec := marshaler.NewDecoder(req.Body)
 	handleSend := func() error {
 		var protoReq {{.Method.RequestType.GoType .Method.Service.File.GoPkg.Path}}
 		err := dec.Decode(&protoReq)

examples/proto/examplepb/stream.pb.gw.go

@@ -391,9 +391,6 @@ func TestApplyTemplateRequestWithClientStreaming(t *testing.T) {
 		if want := spec.sigWant; !strings.Contains(got, want) {
 			t.Errorf("applyTemplate(%#v) = %s; want to contain %s", file, got, want)
 		}
-		if want := `marshaler.NewDecoder(newReader()`; !strings.Contains(got, want) {
-			t.Errorf("applyTemplate(%#v) = %s; want to contain %s", file, got, want)
-		}
 		if want := `func RegisterExampleServiceHandler(ctx context.Context, mux *runtime.ServeMux, conn *grpc.ClientConn) error {`; !strings.Contains(got, want) {
 			t.Errorf("applyTemplate(%#v) = %s; want to contain %s", file, got, want)
 		}
@@ -482,7 +479,7 @@ func TestAllowPatchFeature(t *testing.T) {
 	}
 }
 
-func TestIdentifierCapitalization(t *testing.T){
+func TestIdentifierCapitalization(t *testing.T) {
 	msgdesc1 := &protodescriptor.DescriptorProto{
 		Name: proto.String("Exam_pleRequest"),
 	}
@@ -492,12 +489,12 @@ func TestIdentifierCapitalization(t *testing.T){
 	meth1 := &protodescriptor.MethodDescriptorProto{
 		Name:       proto.String("ExampleGe2t"),
 		InputType:  proto.String("Exam_pleRequest"),
-		OutputType: proto.String("example_response"),	
+		OutputType: proto.String("example_response"),
 	}
 	meth2 := &protodescriptor.MethodDescriptorProto{
 		Name:       proto.String("Exampl_eGet"),
 		InputType:  proto.String("Exam_pleRequest"),
-		OutputType: proto.String("example_response"),	
+		OutputType: proto.String("example_response"),
 	}
 	svc := &protodescriptor.ServiceDescriptorProto{
 		Name:   proto.String("Example"),