Reading password from stdin does not work

[beep-beep-beep-boop]

It looks like in #12 support was added for reading pw from stdin, but this isn't working for me.

$ echo 12345678 | minisign -G -s my-key.key -p my-key.pub
Please enter a password to protect the secret key.

Password:
Password (one more time): get_password()

It then exits, and no keys are saved on the disk.