Ensure promises are awaited (or have `.catch(...)` installed) within same tick

README.md

In node v8 the code in test.js will result in the following:

(node:47866) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): Error: Thrown error
(node:47866) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
Error: Thrown error
    at foo (/Users/benjiegillam/Documents/test/test.js:2:9)
    at Object.<anonymous> (/Users/benjiegillam/Documents/test/test.js:5:17)
    at Module._compile (module.js:612:30)
    at Object.Module._extensions..js (module.js:623:10)
    at Module.load (module.js:531:32)
    at tryModuleLoad (module.js:494:12)
    at Function.Module._load (module.js:486:3)
    at Function.Module.runMain (module.js:653:10)
    at startup (bootstrap_node.js:187:16)
    at bootstrap_node.js:608:3
(node:47866) PromiseRejectionHandledWarning: Promise rejection was handled asynchronously (rejection id: 1)

Note the "Unhandled promis rejection" warnings because there was no rejection handler installed on the promise result within the same tick - it wasn't until the next tick that the handler was installed (which then results in the "rejection was handled asynchronously" warning.

In future node versions this will cause Node to exit before the error is even handled.

test.js

async function foo() {
  throw new Error("Thrown error");
}

const promise = foo();
setImmediate(async function bar() {
  try {
    await promise;
  } catch (e) {
    console.error(e);
  }
});