insert query not working in golang - mysql

Question

In my golang program, the insert MySQL query was not inserting the values. Even the syntax of the query was correct.It returns my error statement ie internal server error
package main
import (
"database/sql"
"net/http"
"log"
"golang.org/x/crypto/bcrypt"
"encoding/json"
_ "github.com/go-sql-driver/mysql"
"fmt"
)
const hashCost = 8
var db *sql.DB
func initDB(){
var err error
// Connect to the db
//you might have to change the connection string to add your database credentials
db, err = sql.Open("mysql",
"root:nfn#tcp(127.0.0.1:3306)/mydb")
if err != nil {
panic(err)
}
}
// Create a struct that models the structure of a user, both in the request body, and in the DB
type Credentials struct {
Password string `json:"password", db:"password"`
Username string `json:"username", db:"username"`
}
func Signup(w http.ResponseWriter, r *http.Request){
// Parse and decode the request body into a new `Credentials` instance
creds := &Credentials{}
err := json.NewDecoder(r.Body).Decode(creds)
if err != nil {
// If there is something wrong with the request body, return a 400 status
w.WriteHeader(http.StatusBadRequest)
return
}
// Salt and hash the password using the bcrypt algorithm
// The second argument is the cost of hashing, which we arbitrarily set as 8 (this value can be more or less, depending on the computing power you wish to utilize)
hashedPassword, err := bcrypt.GenerateFromPassword([]byte(creds.Password), 8)
// Next, insert the username, along with the hashed password into the database
// Sql query not working Here.How to solve this error
if _, err = db.Exec("INSERT INTO users(username,password) VALUES (?,?) ", creds.Username, string(hashedPassword)); err != nil {
// If there is any issue with inserting into the database, return a 500 error
w.WriteHeader(http.StatusInternalServerError)
return
}
// We reach this point if the credentials we correctly stored in the database, and the default status of 200 is sent back
}