So from what I can tell this is not in any way a security issue or anything new. If you can LD_PRELOAD a library when running a system executable, then you can backdoor it trivially since LD_PRELOAD is designed to allow you to substitute existing symbols with your own symbols. The use of go here matters not at all, and this is not an attack against system executables that use go.

Of course, you can't, as an ordinary user, start system executables with elevated privileges and set LD_PRELOAD.