Upgrading npm when using `asdf` with `reshim`

The version of npm that comes with nodejs when installed with asdf may not be the latest. In my case I had npm 5.3.0 installed and the newest version is 5.4.2. I upgraded npm with npm install -g npm and saw output that made me think everything installed successfully, but when I ran npm -v I still got 5.3.0.

The answer is to use asdf's reshim command.

> asdf help reshim
asdf reshim <name> <version>    Recreate shims for version of a package

I ran the following command:

> npm -v
5.3.0
> asdf reshim nodejs
> npm -v
5.4.2

And now I have the latest version and everything is great!