To avoid this annoying requirement, you can edit /etc/sudoers and add this command at the end of the file:
%admin ALL=(ALL) NOPASSWD: ALL
Save and exit. Finally, you will also need to create the admin group:
and again, you need to be part of the admin group. So type this command in a shell:
# usermod -a -G admin <your username>
You should be able to use sudo without password.