Here is what happens:
var test = "he";
var test2 = "llo";
OUTPUTS: hello. You are using integers as strings.
Therefore you need to convert your variables to int before adding them.
Here is an example:
highestBidAmount = parseInt(highestBidAmount, 10);
Sidenote: Don't change the 10 ...
Think of your VM like a completely different machine. It has another IP for example.
127.0.0.1 accesses localhost and therefore your host machine.
So how do you fix this?
You need to connect to your VM with the correct IP. Go into your VM and run the command ifconfig.
A lot of stuff gets returned. You will surely recognice the correct IP when you see it. ...
You can follow this link. It has explanation on various parts of Ethereum Source code in golang. (Transaction processing, networking, mining issues etc)
Hope it will help you.