Chapter 1

Your First Program

As part of the tradition, the first program will be to print out "Hello World!" in your terminal.

mkdir chapter-01
cd chapter-01
touch main.go

After we have created our first program - "Hello World!", let's compile and run the program:

go run main.go

The go run command compiles the program into an executable saved in a temporary directory and then runs it. In case you want to learn more about the comamnd you can simply execute go help run in the terminal.

Another useful command is go doc fmt Println, which prints the documentation comments associated with Println from the fmt package:

package fmt // import "fmt"

func Println(a ...any) (n int, err error)
    Println formats using the default formats for its operands and writes to
    standard output. Spaces are always added between operands and a newline
    is appended. It returns the number of bytes written and any write error
    encountered.

Problems

1. What is a whitespace?

Newlines, spaces and tabs are known as whitespace (because you cannot see them).

2. What is a comment? What are the two ways of writing a comment?

Comments are ignored by the Go compiler and are there for your own sake. There are 2 types of comments:

• // - single-line commments
• /* */ - multi-line comments

3. Our program began with package main. What would the files in the fmt package begin with?

package fmt

4. We used the Println function defined in the fmt package. If we wanted to use the Exit funtion from the os package what would we need to do?

os.Exit()

5. Modify the program we wrote so that instead of printing Hello World! it prints Hello, my name is followed by your name

package main

import "fmt"

// this is a comment

func main() {
    fmt.Println("Hello, my name is MV.")
}