Set PORT via process.env, not in the exec cmd
Set PORT via process.env, not in the exec cmd

Setting the env variable in cmd line as it was (PORT=port) didn't
work on Windows and to make this kind of solution cross-platform,
would need to do some if-else'ing to do the Right Thing on each
platform. This use of process.env should work fine in all platforms.

dwyl/learn-json-web-tokens,dwyl/learn-json-web-tokens