Variables with :=
Create a variable the Go way.
1package main
2
3import "fmt"
4
5func main() {
6 message := "Hi there"
7 fmt.Println(message)
8}
$ go run main.go
Hi there
Every line, explained
package main- Every Go file starts by saying which package it belongs to. package main means "this is a program you can run", and Go will look inside it for func main.
import "fmt"- import brings in a package from Go's standard library. "fmt" (short for format) is the one full of printing tools, like fmt.Println.
func main() {- func main() { ... } is where a Go program starts. When you run the program, Go finds func main inside package main and runs everything between its braces, top to bottom.
message := "Hi there"- := is Go's declare-and-assign: it creates a new variable AND stores a value in one step, and Go works out the type by itself. You will use := constantly in Go. (No semicolon needed; Go adds them for you behind the scenes.) Here it creates message and stores the text "Hi there".
fmt.Println(message)- fmt.Println(...) prints what is inside the brackets to the terminal, then moves to a new line (Println is short for "print line"). The capital P matters: in Go, the tools a package shares all start with a capital letter. No quotes around message, so Go prints what is stored in the variable, not the word message itself.
}- This closing brace } ends func main.