Function Three.
Example function, logs 'hello' and currect context.

@param {Object} context Current context object.
@param {Function} next Next middleware in chain.
function three(context, next) {
  console.log('Hi from three', context);
  setTimeout(function() {
    context.three = 'Hello';
    console.log('Hello from three', context);
  }, 1000);
}