improve handling of variables which contain sensitive data

[equinox0815]

It would be nice to protect variables like passwords and other sensitive data i.e. by clearing the memory before returning it to the kernel. Sadly this is quite complicated with go as it is not possible to know for sure if there are any copies of the variable lying around in memory.
It would be great to at least use syscall.Mlockall(syscall.MCL_FUTURE) but after adding that the app panics... why is this?