How to get a package const value by name using reflect?

It's a package having some constants.

package object

type Languaege int

const (
    Javascript Languaege = iota
    C
    Cpp
    Shell
)

//========================================

how can i get the value of a type Language if I know its name?

package main
func GetConstByName(name String) {
    ....
}
lang := GetConstByName("Shell")

I don't think you can do it except by hand if you want Language to remain a const integer type.

Here is what I would do - make Language implement Stringer which means you can print it too. You can then invert languageMap to turn language strings into Language

Playground link

package main

import "fmt"

type Language int

const (
	Javascript Language = iota
	C
	Cpp
	Shell
)

var languageMap = map[Language]string{
	Javascript: "Javascript",
	C:          "C",
	Cpp:        "Cpp",
	Shell:      "Shell",
}

func (l Language) String() string {
	return languageMap[l]
}

var languageMapReverse map[string]Language

func NewLanguage(languageName string) Language {
	if languageMapReverse == nil {
		languageMapReverse = make(map[string]Language)
		for l, name := range languageMap {
			languageMapReverse[name] = l
		}
	}
	return languageMapReverse[languageName]
}

func main() {
	fmt.Printf("C is %d: %s: %d\n", C, C, NewLanguage("C"))
	fmt.Printf("Shell is %d: %s: %d\n", Shell, Shell, NewLanguage("Shell"))
}

This outputs

C is 1: C: 1
Shell is 3: Shell: 3

You're trying to abuse reflection. In this case, fortunately for you, it will not work. If you want to map string keys to some associated values then use a map[string]someValueType instead.