package main

import (
    "encoding/json"
    "fmt"
)

func main() {
    data := `{"url": "testphp.vulnweb.com"}`

    var m map[string]json.RawMessage
    err := json.Unmarshal([]byte(data), &m)
    if err != nil {
        fmt.Println(err)
        return
    }

    // Printing the raw message byte array
    fmt.Printf("RawMessage in bytes: %v\n", m["url"])

    // Decode the "url" field
    var url string
    err = json.Unmarshal(m["url"], &url)
    if err != nil {
        fmt.Println(err)
        return
    }

    fmt.Printf("Original RawMessage: %s\n", string(m["url"]))
    fmt.Printf("Parsed URL: %s\n", url)
}

RawMessage in bytes: [34 116 101 115 116 112 104 112 46 118 117 108 110 119 101 98 46 99 111 109 34]
Original RawMessage: "testphp.vulnweb.com"
Parsed URL: testphp.vulnweb.com