Go programs have a simple, understandable structure. This structure includes a few basic parts, which we'll go over below:

• Packages
• Adding packages (import)
• The main package and function
• Comments
• Case sensitivity
• Running a program
• Compiling a program

Packages

In Go, we use directories (folders) and files to organize code. Each directory (folder) can have one or more files.

Each directory corresponds to one package, and the content of each file starts with a package statement. The package statement shows which package the file belongs to, so the name we specify with the package statement should preferably match the name of the directory the file is in.

As in the image above, suppose we have two directories (folders) named foo and bar. Each of these directories contains a number of Go files. The first line of each file specifies the name of the package that file belongs to. In most cases, the package's name should match the name of the directory the source code file is in.

Adding Packages (import)

If we're in package foo and want to use things we defined in package bar, we first need to import package bar. We can do the importing either individually or as a group.

package foo

// single import
import "bar"

// group import
import (
	"log"
	"fmt"
)

The main Package and Function

Every Go program has a function named main, which sits inside a package named main. Go programs start running from this main function.

package main

func main() {
	// entry point of a Golang application
}

Comments

Comments are textual notes placed in a program's code. Comments are used to document code, explain how it works, or note down important reminders. In Go, comments come in two forms: single-line and multi-line.

Single-line comments start with two slashes (//). On any line of code, everything after these marks, up to the end of that line, is treated as a comment.

package main

import "fmt"

func main() {
    // print a message to the console
    fmt.Println("Hello, World!") // this is a welcome message
}