Update go dep (#1560)

This fix updates go dep with `dep ensure --update` as well as the following:
- Removed github.com/ugorji/go restriction in Gopkg.toml (fixes  #1557)
- Added github.com/flynn/go-shlex in Makefile (neede by Caddy, maybe removed later)

This fix fixes #1557

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

vendor/google.golang.org/grpc/server.go

@@ -40,6 +40,7 @@ import (
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/credentials"
 	"google.golang.org/grpc/encoding"
+	"google.golang.org/grpc/encoding/proto"
 	"google.golang.org/grpc/grpclog"
 	"google.golang.org/grpc/internal"
 	"google.golang.org/grpc/keepalive"
@@ -105,7 +106,7 @@ type Server struct {
 
 type options struct {
 	creds                 credentials.TransportCredentials
-	codec                 Codec
+	codec                 baseCodec
 	cp                    Compressor
 	dc                    Decompressor
 	unaryInt              UnaryServerInterceptor
@@ -182,6 +183,8 @@ func KeepaliveEnforcementPolicy(kep keepalive.EnforcementPolicy) ServerOption {
 }
 
 // CustomCodec returns a ServerOption that sets a codec for message marshaling and unmarshaling.
+//
+// This will override any lookups by content-subtype for Codecs registered with RegisterCodec.
 func CustomCodec(codec Codec) ServerOption {
 	return func(o *options) {
 		o.codec = codec
@@ -327,10 +330,6 @@ func NewServer(opt ...ServerOption) *Server {
 	for _, o := range opt {
 		o(&opts)
 	}
-	if opts.codec == nil {
-		// Set the default codec.
-		opts.codec = protoCodec{}
-	}
 	s := &Server{
 		lis:   make(map[net.Listener]bool),
 		opts:  opts,
@@ -695,7 +694,7 @@ func (s *Server) serveUsingHandler(conn net.Conn) {
 // available through grpc-go's HTTP/2 server, and it is currently EXPERIMENTAL
 // and subject to change.
 func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-	st, err := transport.NewServerHandlerTransport(w, r)
+	st, err := transport.NewServerHandlerTransport(w, r, s.opts.statsHandler)
 	if err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return
@@ -759,7 +758,7 @@ func (s *Server) sendResponse(t transport.ServerTransport, stream *transport.Str
 	if s.opts.statsHandler != nil {
 		outPayload = &stats.OutPayload{}
 	}
-	hdr, data, err := encode(s.opts.codec, msg, cp, outPayload, comp)
+	hdr, data, err := encode(s.getCodec(stream.ContentSubtype()), msg, cp, outPayload, comp)
 	if err != nil {
 		grpclog.Errorln("grpc: server failed to encode response: ", err)
 		return err
@@ -904,7 +903,7 @@ func (s *Server) processUnaryRPC(t transport.ServerTransport, stream *transport.
 			// java implementation.
 			return status.Errorf(codes.ResourceExhausted, "grpc: received message larger than max (%d vs. %d)", len(req), s.opts.maxReceiveMessageSize)
 		}
-		if err := s.opts.codec.Unmarshal(req, v); err != nil {
+		if err := s.getCodec(stream.ContentSubtype()).Unmarshal(req, v); err != nil {
 			return status.Errorf(codes.Internal, "grpc: error unmarshalling request: %v", err)
 		}
 		if inPayload != nil {
@@ -996,7 +995,7 @@ func (s *Server) processStreamingRPC(t transport.ServerTransport, stream *transp
 		t:     t,
 		s:     stream,
 		p:     &parser{r: stream},
-		codec: s.opts.codec,
+		codec: s.getCodec(stream.ContentSubtype()),
 		maxReceiveMessageSize: s.opts.maxReceiveMessageSize,
 		maxSendMessageSize:    s.opts.maxSendMessageSize,
 		trInfo:                trInfo,
@@ -1262,6 +1261,22 @@ func init() {
 	}
 }
 
+// contentSubtype must be lowercase
+// cannot return nil
+func (s *Server) getCodec(contentSubtype string) baseCodec {
+	if s.opts.codec != nil {
+		return s.opts.codec
+	}
+	if contentSubtype == "" {
+		return encoding.GetCodec(proto.Name)
+	}
+	codec := encoding.GetCodec(contentSubtype)
+	if codec == nil {
+		return encoding.GetCodec(proto.Name)
+	}
+	return codec
+}
+
 // SetHeader sets the header metadata.
 // When called multiple times, all the provided metadata will be merged.
 // All the metadata will be sent out when one of the following happens: