HTTP POST error: Post "": unsupported protocol scheme ""

[devashishraj]

i have created the following config.json file

{
    "serverinfo": {
        "url": "http://<ip:port>/rpi"
    }
}

earlier it was hardcoded via a variable and passed into :

resp, err := http.Post(serverUrl, "application/json", bytes.NewBuffer(jsonData))
	if err != nil {
		log.Fatalln("HTTP POST error:", err)

	}

now i treid using viper to store the serverUrl , now running the executable leads to following error

 HTTP POST error: Post "": unsupported protocol scheme ""

relevant code snippet :

serverUrl := viper.GetString("serverinfo.url")
	serverUrl = string(serverUrl)

	fmt.Println(serverUrl)
	//log.Fatalln(" serverUrl to string assertion failed")

	// Convert the struct to JSON
	jsonData, err := json.Marshal(sysinfo)
	if err != nil {
		fmt.Println("Error marshaling JSON:", err)
	}

	// https://github.com/spf13/viper#getting-values-from-viper

	resp, err := http.Post(serverUrl, "application/json", bytes.NewBuffer(jsonData))
	if err != nil {
		log.Fatalln("HTTP POST error:", err)

	}

NOTE: i added println for serverUrl to check if serverurl had some some value or not and it's empty