Error injecting ssh key

I am unable to add SSH key to Docker, every time it gives an error-

C:\Users\anoop>pygmy addkey
docker: Error response from daemon: invalid mode: /Users/anoop/.ssh/id_rsa.
See ‘docker run --help’.
Error adding ssh key

I had already added path in Docker’s Resource share option. Also I had regenerated SSH key from command prompt but it is still not working.