Update to use go modules (#671)

This includes updates to CI config, vendor files, etc.
I've hard-coded the k8s depedency at 1.13.4 to keep it inline with what
we currently have and to make sure a another run of `go mod tidy`
doesn't accidentally update it to an unexpected version.

Thanks to hectorj2f for carrying this along.

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

@@ -28,6 +28,7 @@
 package status
 
 import (
+	"context"
 	"errors"
 	"fmt"
 
@@ -126,7 +127,9 @@ func FromError(err error) (s *Status, ok bool) {
 	if err == nil {
 		return &Status{s: &spb.Status{Code: int32(codes.OK)}}, true
 	}
-	if se, ok := err.(interface{ GRPCStatus() *Status }); ok {
+	if se, ok := err.(interface {
+		GRPCStatus() *Status
+	}); ok {
 		return se.GRPCStatus(), true
 	}
 	return New(codes.Unknown, err.Error()), false
@@ -182,8 +185,26 @@ func Code(err error) codes.Code {
 	if err == nil {
 		return codes.OK
 	}
-	if se, ok := err.(interface{ GRPCStatus() *Status }); ok {
+	if se, ok := err.(interface {
+		GRPCStatus() *Status
+	}); ok {
 		return se.GRPCStatus().Code()
 	}
 	return codes.Unknown
 }
+
+// FromContextError converts a context error into a Status.  It returns a
+// Status with codes.OK if err is nil, or a Status with codes.Unknown if err is
+// non-nil and not a context error.
+func FromContextError(err error) *Status {
+	switch err {
+	case nil:
+		return New(codes.OK, "")
+	case context.DeadlineExceeded:
+		return New(codes.DeadlineExceeded, err.Error())
+	case context.Canceled:
+		return New(codes.Canceled, err.Error())
+	default:
+		return New(codes.Unknown, err.Error())
+	}
+}