Golo supports the traditional if / else constructions, as in:

if goloIsGreat() {
  println("Golo Golo")
}

if (someCondition) {
  doThis()
} else if someOtherCondition {
  doThat()
} else {
  doThatThing()
}

The condition of an if statement does not need parenthesis. You may add some to clarify a more elaborated expression, though.