Custom unmarshaling to a temporary struct

unmarshal.go

package main

type (
  // The struct we actually want to unmarshal to
  MyStruct {
    name string     `yaml:"name"`
    age  int        `yaml:"age"`
    flavour string  `yaml:"flavour"`
  } `yaml:"mystruct"`

  // Temp struct mapping the same fields as the original
  unmarshalMyStuct MyStruct
)

// UnmarshalYAML is called automatically by `yaml.Unmarshal` when attempting
// to unmarshal yaml into an element of the receiver type.
func (m *MyStruct) UnmarshalYAML(unmarshal func(interface{}) error) error {

  // Create an instance of the unmarshaler struct. We use a
  // tempororay middle stage as attempting to unmarshal to the
  // _actual_ type breaks with a stack loop (I believe it recursively
  // keeps calling this function and unmarshaling to itself again
  // until the maximum call stack is reached)
  var u unmarshalMyStruct

  // Run the actual unmarshal to the temporary struct
  if err := unmarshal(&u); err != nil {
      return err
  }

  // Map the unmarshaled struct type back to the original
  // so's the correct value is populated in the parent.
  *m = MyStruct(u)
  return nil
}

// ... main() and other functions omitted