What is this ?

This is my solution to the Tendermint Alien Invasion Technical Challenge, briefly described here:

"Mad aliens are about to invade the earth and you are tasked with simulating the invasion. These aliens start out at random places on the map, and wander around randomly, following links. Each iteration, the aliens can travel in any of the directions leading out of a city. When two aliens end up in the same place, they fight, and in the process kill each other and destroy the city. When a city is destroyed, it is removed from the map, and so are any roads that lead into or out of it. Once a city is destroyed, aliens can no longer travel to or through it. You should create a program that reads in the world map, creates N aliens, and unleashes them. The program should run until all the aliens have been destroyed, or each alien has moved at least 10,000 times."

Input
The city and each of the pairs are separated by a single space, and the directions are separated from their respective cities with an equals (=) sign.
For example:

Foo north=Bar west=Baz south=Qu-ux
Bar south=Foo west=Bee

Architecture / Design

This program consists of 3 structs namely: city,world, and alien structs, each of which has methods and fields that are used/referenced in the main invasion.go program file.

Tests

Test files can be found in invasion_test.go and in the tests folder. The tests folder contains all of the made-up test worlds, namely:

1. Symmetric World :
   In this world, all bridges are bidirectional.
2. Asymmetric World
   In this world, there are no bidirectional bridges.
3. Symmetry Combination World
   In this world there is a combination of bidirectional and single directional bridges.
4. One-Liner World In this world there is only one "non-trap" city (A trap city is one which has no bridges leading out of the city)
5. Stress World:
   In this world there is a combination of single directional and bidirectional birdges on larger number of cities in a more complex arrangement.

Each of these worlds are tested with launch parties of varying sizes listed below:

1. 0
2. a size less than the number of cities in the world to be tested
3. the same number of aliens as there are cities in the world to be tested
4. more aliens than there are cities in the world to be tested.

Assumptions

Assumption 1:
Each city name is unique. There will be no 2 cities with the same name

Assumption 2: For each direction (north, south,east, west), there will be at most 1 city in that direction. in other words, there can not be a road in any direction that leads to multiple cities in terms of our input, this means that "Foo north=Bar,Bee" is not a valid input

Assumption 3: all inputted world_maps meet the aforementioned standards/requirements of a the world, such as no multiple destinations from the same road, cities names are all string and do not contain numbers (int or float), and the syntactical requirements of the input is met as specified in the problem specifics detailed in the alien_invasion pdf document.

Assumption 4: All inputs make geographical sense, meaning that, for example: there will be no input such that Foo.North = Bar, and Bar.North = Foo.

Assumption 5: No need to filter for invalid input. We will assume that all input is valid in terms or character/string capitalization, white spaces, equal signs, etc.

Assumption 6:
The number of aliens inputted in the command line argument will not be negative, and also will not be greater than the maximum integer value in GoLang

How To Use

1. Fork/Clone Repository
2. To run tests, run the following on the command line:
   test go -run NameOfTest
3. To run program, run the following on the command line:
   go run invasion.go << NumberOfAliens >>
   where << NumberOfAliens >> is your desired alien launch party size. The default world is the Symmetry Combination World. This may be modified by changing the input filepath in the read function in invasion.go