glide can't get newest version of golang.org/x/sys

[zhyon404]

google.golang.org/grpc need newest version of golang.org/x/sys, otherwise it report

src/vendor/google.golang.org/grpc/internal/channelz/types_linux.go:41:15: undefined: unix.GetsockoptLinger
src/vendor/google.golang.org/grpc/internal/channelz/types_linux.go:44:15: undefined: unix.GetsockoptTimeval
src/vendor/google.golang.org/grpc/internal/channelz/types_linux.go:47:15: undefined: unix.GetsockoptTimeval

after glide up, glide get ebfc5b4631820b793c9010c87fd8fef0f39eb082 which is left behind 4 commit. currently i set golang.org/x/sys newest version and run glide install to solve this problem.