How do I Parse YAML Files in Go?

Parsing YAML Files in Go

Parsing YAML files in Go requires understanding the structure of the data and the appropriate data types to represent it.

Example: Parsing a Firewall Network Rules File

Consider the following YAML file with firewall network rules:

---
firewall_network_rules:
  rule1:
    src:       blablabla-host
    dst:       blabla-hostname
...

To parse this file, we'll define a Config struct to represent the YAML contents:

type Config struct {
    Firewall_network_rules map[string][]string
}

We'll then use the yaml package to unmarshal the YAML file into the Config struct:

func main() {
    filename, _ := filepath.Abs("./fruits.yml")
    yamlFile, err := ioutil.ReadFile(filename)

    if err != nil {
        panic(err)
    }

    var config Config

    err = yaml.Unmarshal(yamlFile, &config)
    if err != nil {
        panic(err)
    }

    fmt.Printf("Value: %#v\n", config.Firewall_network_rules)
}

This approach works because the YAML file uses a nested map structure that corresponds to the Config struct.

Example: Parsing a Service YAML File

To parse a more complex YAML file like a Kubernetes service manifest, we'll create a more complex struct:

type Service struct {
    APIVersion string `yaml:"apiVersion"`
    Kind       string `yaml:"kind"`
    Metadata   struct {
        Name      string `yaml:"name"`
        Namespace string `yaml:"namespace"`
        Labels    struct {
            RouterDeisIoRoutable string `yaml:"router.deis.io/routable"`
        } `yaml:"labels"`
        Annotations struct {
            RouterDeisIoDomains string `yaml:"router.deis.io/domains"`
        } `yaml:"annotations"`
    } `yaml:"metadata"`
    Spec struct {
        Type     string `yaml:"type"`
        Selector struct {
            App string `yaml:"app"`
        } `yaml:"selector"`
        Ports []struct {
            Name       string `yaml:"name"`
            Port       int    `yaml:"port"`
            TargetPort int    `yaml:"targetPort"`
            NodePort   int    `yaml:"nodePort,omitempty"`
        } `yaml:"ports"`
    } `yaml:"spec"`
}

We'll then unmarshal the YAML file into this struct:

var service Service

err = yaml.Unmarshal(yourFile, &service)
if err != nil {
    panic(err)
}

fmt.Print(service.Metadata.Name)

By using appropriate structs that match the YAML structure, we can effectively parse and represent complex YAML data in Go.

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