👣 Print struct variables in Go

Standard fmt.Print() does not print variable names of Go structs, but it does not mean you cannot do that. To print struct variables in Go, you can use the following methods:

Use fmt.Printf() with format “verbs” %+v or %#v.
Convert the struct to JSON and print the output.
Use external packages to pretty-print structs, for example, go-spew.

See the example below and compare these three options.

package main

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

    "github.com/davecgh/go-spew/spew"
)

type Fruit struct {
    Name    string
    color   string
    Similar *Fruit
}

func main() {
    strawberry := Fruit{
        Name:    "strawberry",
        color:   "red",
        Similar: nil,
    }

    raspberry := Fruit{
        Name:    "raspberry",
        color:   "pink",
        Similar: &strawberry,
    }

    // fmt.Printf with format verbs
    fmt.Printf("fmt.Printf with format verbs\n")
    fmt.Printf("%+v\n%#v\n", raspberry, raspberry)

    // json encoding
    fmt.Printf("---\njson encoding\n")
    jsonData, err := json.Marshal(&raspberry)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(string(jsonData))

    // go-spew
    fmt.Printf("---\ngo-spew\n")
    spew.Dump(raspberry)
}

Output:

fmt.Printf with format verbs
{Name:raspberry color:pink Similar:0xc000070390}
main.Fruit{Name:"raspberry", color:"pink", Similar:(*main.Fruit)(0xc000070390)}
---
json encoding
{"Name":"raspberry","Similar":{"Name":"strawberry","Similar":null}}
---
go-spew
(main.Fruit) {
 Name: (string) (len=9) "raspberry",
 color: (string) (len=4) "pink",
 Similar: (*main.Fruit)(0xc000070390)({
  Name: (string) (len=10) "strawberry",
  color: (string) (len=3) "red",
  Similar: (*main.Fruit)(<nil>)
 })
}

Note the differences:

fmt.Printf() prints only field values, which in the case of a pointer, it is the memory address of the variable it points to.
Encoding to JSON requires all struct fields to be exported (the first letter capitalized). Otherwise, unexported fields such as color will not appear in the resulting JSON.
Package go-spew prints detailed information about the struct, but it is an external dependency that needs to be imported.

Depending on your use case, you should choose the method that suits you best.