Move handlers so they are lazy loaded

[tclindner]

Hey @marconi1992 - This PR moves the handlers so they are lazy loaded (as discussed in #6). Please let me know if you have any questions.

Closes #5
Closes #6

[marconi1992]

It works!! thank you!! we can improve it to avoid load the function options every time the lambda is invoked.

[marconi1992]

I think the function options should be only loaded when serverless offline runs the first time, and also we should create the handler when the lambda function needs to be invoked to hot reload it.

outside the route

const funOptions = Object.keys(this.service.functions).reduce((acc, key) => {
      const fun = this.service.getFunction(key);
      acc[key] = functionHelper.getFunctionOptions(fun, key, servicePath, serviceRuntime);
      return acc;
    }, {});

into the route

const options = funOptions[functionName];

if (!options) {
   return reply().code(404);
}

const handler = functionHelper.createHandler(options, {});

[tclindner]

Sounds good to me 👍 Thank you for looking through the PR!

[marconi1992]

This handler constant is not necessary anymore, we should remove it

[tclindner]

Updated. Would you be open to adding a linter to help detect things like that?

[marconi1992]

We already have an ESlint configuration and npm script to run it: https://github.com/marconi1992/serverless-offline-lambda/blob/master/package.json#L11

I'd like to add a CI/CD. I'll create an issue to address that.