Variables & Assignment

Code

Create main.go — your fields become variables

Replace the contents of your main.go with this (the sample continues the book-list thread from lesson 1; your fields will differ). All three forms in one place:

const appName — at file level: the app's name never changes.
var title string = ... — the full form with an explicit type.
pages := 380 and read := false — the short form; Go infers int and bool.

The new thing is fmt.Printf with format verbs: %s inserts text, %d an integer, %v anything (handiest for bool). The \n at the end is a newline.

Verify.

go run main.go

You must see exactly:

App: Book list
Book: The Go Programming Language | pages: 380 | read: false

Tip. Try to break it: inside the function write pages := "many" after pages is already an int — the compiler refuses. Go types are fixed: born a number, stays a number.

main.go CREATE

Create this file in ./

package main

import "fmt"

// appName never changes while the program runs — a constant.
const appName = "Book list"

func main() {
	// Last lesson you wrote your fields on paper — now they are variables.
	var title string = "The Go Programming Language" // full form: var + name + type
	pages := 380                                     // short form: type inferred (int)
	read := false                                    // bool: true or false

	fmt.Println("App:", appName)
	fmt.Printf("Book: %s | pages: %d | read: %v\n", title, pages, read)
}