Extensible nested yaml fields in golang

gistfile1.txt

```
package main

import (
	"fmt"
	"os"

	"gopkg.in/yaml.v2"
)

var indata string = `
version: 1
field1: "value1"
nest:
  nestF1: v1
  nestF2: |
   Four score and seven years ago,
   our fathers...
`

type yaml1 struct {
	Version string      `yaml:"version"`
	Field1  string      `yaml:"field1"`
	Nested   interface{} `yaml:"nest"`
}

type wrappedYaml struct {
	Field1 string `yaml:"nestF1"`
	Field2 string `yaml:"nestF2"`
}

func main() {
	c := []byte(indata)
	fmt.Printf("c is %v\n", c)
	struct1 := &yaml1{}
	err := yaml.Unmarshal(c, struct1)
	if err != nil {
		fmt.Printf("unmarshall error %v\n", err)
		os.Exit(1)
	}
	fmt.Printf("struct1 is is %v\n", struct1)
	struct2 := struct1.Nested.(map[interface{}]interface{})
	fmt.Printf("wrapped field1 is %v\n", struct2)
	fmt.Printf("struct2.Field1 is %s\n", struct2["nestF1"])
	fmt.Printf("struct2.Field2 is %s\n", struct2["nestF2"])
}
```