Making Decisions with if and else

So far your programs run the same steps every time. Real programs react: show this page if the user is logged in, warn if the password is too short. In Go, decisions are made with if.

The shape of an if

score := 75

if score >= 50 {
    fmt.Println("You passed!")
}

The condition score >= 50 is a question with a true or false answer. If it is true, the steps inside the braces run. If not, Go skips them. Two style notes that surprise people coming from other languages:

• No parentheses around the condition. Go likes it bare.
• The braces { } are always required, even for a single line.

else and else if

score := 91

if score >= 90 {
    fmt.Println("Amazing!")
} else if score >= 50 {
    fmt.Println("Nice work, you passed.")
} else {
    fmt.Println("Keep practicing, you will get there.")
}

Go checks the conditions from top to bottom and runs the first branch whose condition is true, then skips the rest. The final else is the catch-all when nothing above matched.

The comparison operators

• == equal to, and != not equal to
• < and > less than and greater than
• <= and >= less than or equal, greater than or equal

Combining questions

You can join conditions with && (and), || (or), and flip one with ! (not):

age := 13
hasTicket := true

if age >= 12 && hasTicket {
    fmt.Println("Welcome aboard!")
}

With && both sides must be true. With || at least one side must be true.

A handy Go trick: if with a setup step

Go lets you do a small setup right inside the if, separated by a semicolon:

if total := 6 * 7; total > 40 {
    fmt.Println("Big total:", total)
}

Here total is created just for this if and its branches. You will see this pattern all over real Go code, especially for handling errors later.