go で yaml 等を「map[interface{}]interface{}」型で読み込んだ際の動的型の参照方法 ref: http://qiita.com/yamasaki-masahide/items/d6e406c4c11d5870a1c6

config

mail_from: hoge@fuga.com
to: [hoge@fuga.com]
var:
  c: 2
  d: [3, 4]

example.go

    m := make(map[interface{}]interface{})
    err = goyaml.Unmarshal([]byte(config), &m)
    if err != nil {
        panic(err)
    }
    //fmt.Printf("--- m:\n%# v\n\n", m)
    pretty.Printf("--- m:\n%# v\n\n", m)

file2.txt

$ go run main.go
--- m:
map[interface {}]interface {}{
    "mail_from": "hoge@fuga.com",
    "to":        []interface {}{
        "hoge@fuga.com",
    },
    "var": map[interface {}]interface {}{
        "c": int(2),
        "d": []interface {}{
            int(3),
            int(4),
        },
    },
}

file3.go

fmt.Printf("--- m.to:\n%# v\n\n", m["to"])

file4.go

fmt.Printf("--- m.var.c:\n%# v\n\n", m["var"]["c"])

file5.go

fmt.Printf("--- m.var.c:\n%# v\n\n", m["var"].(map[interface {}]interface {})["c"])