Why is my YAML unmarshaling to an empty struct?

Unmarshaling YAML into Struct: Understanding Unexported Fields

In this code, you're attempting to parse a YAML document into a Config struct. However, the resulting config struct remains empty, as indicated by {}. This is because your struct fields are unexported.

Solution: Exporting Struct Fields

YAML Unmarshaling requires the struct fields to be exported (starting with uppercase letters) so that it can access and populate them. Here's the corrected code:

type Config struct {
    FooBar string `yaml:"foo_bar"`
}

Understanding Exported Fields

In Go, exported fields are accessible outside the package where they're declared. This means that fields starting with uppercase letters can be accessed by other packages or code. Conversely, unexported fields (starting with lowercase letters) are only accessible within the same package.

When YAML Unmarshaling is performed, the exported fields are identified and populated from the YAML data. Since your original fields were unexported, YAML Unmarshaling couldn't access them and left them empty.

Corrected Code

After updating the struct fields to be exported, the code will successfully parse the YAML data and populate the config struct:

type Config struct {
    FooBar string `yaml:"foo_bar"`
}

func main() {
    config := ParseYAMLConfig([]byte(configYAMLData))
    fmt.Printf("%v", config) // Outputs: {https://foo.bar}
}

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