With additional plugins:
Once you install it, just hit <kbd>ALT+R</kbd> to run the file. Note that this may collide with the go-plus plugin's Rename functionality. You may change any of the key bindings in Atom's settings (change one of them to be unique to your liking). If you don't want to change keybindings, you may use Atom's Command Palette: press <kbd>CTRL+SHIFT+P</kbd>, then type "run" or "run file", and it will be the first or second item.
Installing this gives you an internal terminal. Click the plus icon at the bottom, which opens a terminal. You can configure it to open a terminal having the working directly of the current file, so after that all you need is to type go run xx.go
. You may also "fast-open" the terminal by pressing <kbd>ALT+SHIFT+T</kbd>.
Note: platformio-ide-terminal is a fork of terminal-plus, one which did not work for me (and reportedly for others).