Update gRPC and fix tests (#27)

Combines the two open PRs so the tests pass and we don't depend on
outdated gRPC internals.

proxy/handler.go

@@ -9,7 +9,6 @@ import (
 	"golang.org/x/net/context"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
-	"google.golang.org/grpc/transport"
 )
 
 var (
@@ -60,11 +59,10 @@ type handler struct {
 // forwarding it to a ClientStream established against the relevant ClientConn.
 func (s *handler) handler(srv interface{}, serverStream grpc.ServerStream) error {
 	// little bit of gRPC internals never hurt anyone
-	lowLevelServerStream, ok := transport.StreamFromContext(serverStream.Context())
+	fullMethodName, ok := grpc.MethodFromServerStream(serverStream)
 	if !ok {
 		return grpc.Errorf(codes.Internal, "lowLevelServerStream not exists in context")
 	}
-	fullMethodName := lowLevelServerStream.Method()
 	// We require that the director's returned context inherits from the serverStream.Context().
 	outgoingCtx, backendConn, err := s.director(serverStream.Context(), fullMethodName)
 	clientCtx, clientCancel := context.WithCancel(outgoingCtx)

proxy/handler_test.go

@@ -135,7 +135,7 @@ func (s *ProxyHappySuite) TestPingCarriesServerHeadersAndTrailers() {
 	out, err := s.testClient.Ping(s.ctx(), &pb.PingRequest{Value: "foo"}, grpc.Header(&headerMd), grpc.Trailer(&trailerMd))
 	require.NoError(s.T(), err, "Ping should succeed without errors")
 	require.Equal(s.T(), &pb.PingResponse{Value: "foo", Counter: 42}, out)
-	assert.Len(s.T(), headerMd, 1, "server response headers must contain server data")
+	assert.Contains(s.T(), headerMd, serverHeaderMdKey, "server response headers must contain server data")
 	assert.Len(s.T(), trailerMd, 1, "server response trailers must contain server data")
 }
 
@@ -170,7 +170,7 @@ func (s *ProxyHappySuite) TestPingStream_FullDuplexWorks() {
 			// Check that the header arrives before all entries.
 			headerMd, err := stream.Header()
 			require.NoError(s.T(), err, "PingStream headers should not error.")
-			assert.Len(s.T(), headerMd, 1, "PingStream response headers user contain metadata")
+			assert.Contains(s.T(), headerMd, serverHeaderMdKey, "PingStream response headers user contain metadata")
 		}
 		assert.EqualValues(s.T(), i, resp.Counter, "ping roundtrip must succeed with the correct id")
 	}