"sudo must be owned by uid 0" when installing a package

Question

I installed npm and tried to install a package:

npm install -g reaction-cli

I got an error like:

Error: EACCES: permission denied, access '/usr/lib/node_modules'

So, I tried to add permission with:

sudo chown -R $USER /usr/lib

But when I try to install other software, for example

sudo apt-get install git-core

I get:

sudo: error in /etc/sudo.conf, line 0 while loading plugin 
"sudoers_policy" sudo: /usr/lib/sudo/sudoers.so must be owned by uid 0 
sudo: fatal error, unable to load plugins

Is there any method to resolve my problem?

I also using sudo chown -R $USER /src/http to access source in Apache server to edit files. Then I don't get this error.