Golang in sixty seconds — string formatting

If you've done your first go tutorial, it probably went something like this:

fmt.Println("Hello World!") // Hello World!

However if you try to use Println on something more complex than a string, you may get surprising results.

type person struct {
 name string
 age  int
}
fmt.Println(person{name: "Alice", age: 30}) //{Alice 30}

In this example, if you want to print out the keys as well as the values you will need to use a format string.

fmt.Printf("person = %+v", person{name: "Alice", age: 30}) 
    // person = {name:Alice age:30}

%v will print the value in a default format. When printing structs, the plus flag (%+v) adds field names. There are a large number of verbs documented in the official docs.

How to format a string without printing it? You can usefmt.Sprintf instead the same way you would use fmt.Printf.

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