package main

import (  
    "fmt"
    "reflect"
)

func main() {  
    type S struct {
        F string `species:"gopher" color:"blue"`
        E string `species:"golang" color:"black"`
    }

    s := S{}
    st := reflect.TypeOf(s)
    for i := 0; i < st.NumField(); i++ {
        field := st.Field(i)
        fmt.Println(field.Tag.Get("species"))
    }
}