How To Print Struct Fields in Go

The Problem

You don’t know how to see the values that a struct contains.

The Solution

Because struct fields in Go are just values, printing them out can be as simple as printing any variable:

package main

import "fmt"

type Example struct {
	ID    int
	Title string
}

func main() {
	example := Example{
		ID:    42,
		Title: "Example title",
	}

	fmt.Printf("example struct: ID: %d, Title: %s", example.ID, example.Title)

This prints:

example struct: ID: 42, Title: Example title

Printing the Entire Struct

If you want to print the entire struct and include its field names automatically, you can use a special verb to do so:

package main

import (
	"encoding/json"
	"fmt"
	"log"
)

type Example struct {
	ID    int
	Title string
	List  []int
}

func main() {
	example := Example{
		ID:    42,
		Title: "Example title",
		List:  []int{1, 2, 3},
	}

	fmt.Printf("%+v", example)
}

This prints:

{ID:42 Title:Example title List:[1 2 3]}

Alternatively, if you want to print something easier to see over multiple lines, you can use the json.MarshallIndent function to print it as indented JSON:

func main() {
	example := Example{
		ID:    42,
		Title: "Example title",
		List:  []int{1, 2, 3},
	}

	bytes, err := json.MarshalIndent(example, "", "\t")
	if err != nil {
		log.Fatal("failed to marshal example", err)
	}

	fmt.Println(string(bytes))
}

This prints:

{
  "ID": 42,
  "Title": "Example title",
  "List": [
    1,
    2,
    3
  ]
}

Further Reading

• The Go maps in action blog post
• The zero value in the Go Spec
• The empty struct by Dave Cheney