Golang：返回指针并取消引用

Question

So I have a function getToken()

func getToken() jwt.MapClaims {
    tokenString := "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VybmFtZSI6ImFkYW0iLCJwYXNzd29yZCI6InRlc3QiLCJpYXQiOjE0ODcyMDY2OTIsImV4cCI6MTUxODc2NDI5Mn0.6LQo_gRwXiFBvNIJOwtf9UuxoQMZZ3XNILTnU-46-Zg"
    token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {

        if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
            return nil, fmt.Errorf("Unexpected signing method: %v", token.Header["alg"])
        }

        hmacSampleSecret := []byte("supersecretkittysecret")
        return hmacSampleSecret, nil
    })

    if err != nil {
        println("error")
    }

    if claims, ok := token.Claims.(jwt.MapClaims); ok && token.Valid {
        return claims
    } else {
        return nil
    }

}

Then the corresponding call:

res := getToken()

println(res["username"])

Why is res["username"] equal to two memory addresses (0x2b3c20,0xc420075420)? This should just be a string like adam. I have also tried func getToken() *jwt.MapClaims and return &claims, but this still did not help.

Answer 1

You should try using fmt.Println instead of println. Here's an example of printing a map using println vs fmt.Println

package main

import (
    "fmt"
)

func foo() map[string]string {
    return map[string]string{
        "k": "value",
    }
}

func main() {
    res := foo()
    println("Output from println:", res)          // prints pointer address
    fmt.Println("Output from fmt.Println: ", res) // prints the map
}

https://play.golang.org/p/gCNqng3KEE

Output:

Output from println: 0x10432200
Output from fmt.Println:  map[k:value]