In regards to Zerogiven's note about rootless docker compatiblity in issue #143, I've tested this pr in a rootless docker instance and everything works as it should.

one potential problem I see with this addition is that the errors returned and checked are only for writing the file: nothing is ever checked for the permissions being set - or whether that fails/succeeds.

I recommend a follow-up commit that encapsulates os.Chmod(....) in a helper function which actually checks the return values (for errors) and handles them.