YAML in Go

Internal

• Go Code Examples
• Go Structs

Overview

Declare a recursive structure that matches the structure of the YAML file, and then use a YAML encoder/decoder to marshall/unmarshall data in and out.

YAML support is available in the gopkg.in/yaml.v3 package.

If the structure fields are not capitalized, they are not visible across packages, and their content will zero-ed.

Come up with an in-depth explanation for this.

package main

import (
  "fmt"
  "gopkg.in/yaml.v3"
  "os"
)

//
// color: "blue:
// details:
//   size: 10
//   weight 2.2
//   used: true
//   options:
//     - light
//     - medium
//     - heavy
//

type Root struct {
  Color   string  `yaml:"color"`
  Details Details `yaml:"details"`
}

type Details struct {
  Size    int      `yaml:"size"`
  Weight  float64  `yaml:"weight"`
  Used    bool     `yaml:"used"`
  Options []string `yaml:"options"`
}


func main() {

  root := Root{
    Color: "blue",
    Details: Details{
        Size:    10,
        Weight:  2.2,
        Used:    true,
        Options: []string{"light", "medium", "heavy"},
    },
  }

  f, e := os.Create("/Users/ovidiu/tmp/test.yaml")
  if e != nil { ... }

  //
  // Marshal recursive memory struct into a file
  //

  if e := yaml.NewEncoder(f).Encode(&root); e != nil { ... }

  if e = f.Close(); e != nil { ... }
  fmt.Printf("yaml file written and closed\n")

  f, e = os.Open("/Users/ovidiu/tmp/test.yaml")
  if e != nil { ... }
  defer func() {
    if e = f.Close(); e != nil { ... }
  }()

  //
  // Unmarshall the file into a different memory struct
  //
  config2 := Root{}
  if e = yaml.NewDecoder(f).Decode(&config2); e != nil { ... }

  fmt.Printf("%+v\n", config2)
}