gofmt | Engineering Interview Kit

TL;DR

In JavaScript or Python, teams spend hours arguing over tabs vs. spaces, line lengths, and bracket placements. They set up complex Prettier or Black configs. Go solved this by inventing gofmt. It is a built-in formatting tool with strict, unchangeable rules. All Go code in the world looks exactly the same.

Mental Model

How It Works

gofmt parses your source code into an Abstract Syntax Tree (AST) and then prints it back out using standard formatting rules.

The Rules (You cannot change them):

Indentation is strictly done with Tabs, not spaces.
Braces { must be on the same line as the statement, not the next line.
Imports are sorted alphabetically.
Struct fields and variable declarations are vertically aligned.

Every modern IDE (VSCode, GoLand) is configured to run gofmt (or goimports, a slightly smarter wrapper) every time you press Ctrl+S.

Example

Before (Messy):

package main
import "fmt"
func main()      {
x:=10
  if x==10
{
fmt.Println("Ten")}
}

Run the tool:
gofmt -w main.go

After (Perfect):

package main

import "fmt"

func main() {
	x := 10
	if x == 10 {
		fmt.Println("Ten")
	}
}

Common Interview Questions

What is the difference between `gofmt` and `goimports`?

gofmt only formats the syntax. goimports does everything gofmt does, PLUS it automatically manages your import statements. If you type fmt.Println(), goimports will automatically add "fmt" to the top of the file. If you delete the print statement, it will automatically remove "fmt" from the imports so the compiler doesn’t complain. goimports is the industry standard for IDE integration.

What does the `go fmt` command do?

go fmt is just a convenient wrapper around gofmt. While gofmt requires you to specify specific files or directories, running go fmt ./... will format your entire project automatically.