How to Pretty Print JSON Output in Go Using Built-in Functions?

Pretty Printing JSON Output in Go with Built-in Functions

When dealing with JSON output in Go programs, it's often desirable to make it human readable. While jq can be used for this purpose, there are also built-in functions within the Go standard library that can achieve the desired result.

Json Marshal Indenting

The encoding/json package provides the json.MarshalIndent() function for pretty printing JSON output. It takes two additional parameters:

• prefix: The string to add before each line
• indent: The string to add after each level of indentation

By passing an empty string as the prefix and a space as the indent, you can obtain human readable JSON output:

m := map[string]interface{}{"id": "uuid1", "name": "John Smith"}

data, err := json.MarshalIndent(m, "", "  ")
if err != nil {
    panic(err)
}
fmt.Println(string(data))

Output:

{
  "id": "uuid1",
  "name": "John Smith"
}
{
  "id": "uuid1",
  "name": "John Smith"
}

You can also use the json.Encoder.SetIndent() method to set the indentation parameters when using an Encoder:

enc := json.NewEncoder(os.Stdout)
enc.SetIndent("", "  ")
if err := enc.Encode(m); err != nil {
    panic(err)
}

Json Indenting

If you already have a JSON string, you can use the json.Indent() function to format it:

src := `{"id":"uuid1","name":"John Smith"}`

dst := &bytes.Buffer{}
if err := json.Indent(dst, []byte(src), "", "  "); err != nil {
    panic(err)
}
fmt.Println(dst.String())

Output:

{
  "id": "uuid1",
  "name": "John Smith"
}

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