Task: SQL-based authentication
Go: package main

import (
    "bytes"
    "crypto/md5"
    "crypto/rand"
    "database/sql"
    "fmt"

    _ "github.com/go-sql-driver/mysql"
)

func connectDB() (*sql.DB, error) {
    return sql.Open("mysql", "rosetta:code@/rc")
}

func createUser(db *sql.DB, user, pwd string) error {
    salt := make([]byte, 16)
    rand.Reader.Read(salt)
    _, err := db.Exec(`insert into users (username, pass_salt, pass_md5)
        values (?, ?, ?)`, user, salt, saltHash(salt, pwd))
    if err != nil {
        return fmt.Errorf("User %s already exits", user)
    }
    return nil
}

func authenticateUser(db *sql.DB, user, pwd string) error {
    var salt, hash []byte
    row := db.QueryRow(`select pass_salt, pass_md5 from users
        where username=?`, user)
    if err := row.Scan(&salt, &hash); err != nil {
        return fmt.Errorf("User %s unknown", user)
    }
    if !bytes.Equal(saltHash(salt, pwd), hash) {
        return fmt.Errorf("User %s invalid password", user)
    }
    return nil
}

func saltHash(salt []byte, pwd string) []byte {
    h := md5.New()
    h.Write(salt)
    h.Write([]byte(pwd))
    return h.Sum(nil)
}

func main() {
    
    db, err := connectDB()
    defer db.Close()
    createUser(db, "sam", "123")
    err = authenticateUser(db, "sam", "123")
    if err == nil {
        fmt.Println("User sam authenticated")
    }

    
    fmt.Println()
    
    rows, _ := db.Query(`select username, pass_salt, pass_md5 from users`)
    var user string
    var salt, hash []byte
    for rows.Next() {
        rows.Scan(&user, &salt, &hash)
        fmt.Printf("%s %x %x\n", user, salt, hash)
    }
    
    err = createUser(db, "sam", "123")
    fmt.Println(err)
    
    err = authenticateUser(db, "pam", "123")
    fmt.Println(err)
    
    err = authenticateUser(db, "sam", "1234")
    fmt.Println(err)
    
    db.Exec(`truncate table users`)
}

Python: import mysql.connector 
import hashlib
 
import sys	 
import random	 
 
DB_HOST = "localhost"	 
DB_USER = "devel" 
DB_PASS = "devel"	 
DB_NAME = "test"	 
 
def connect_db():	 
    	 
    try:	 
        return mysql.connector.connect(host=DB_HOST, user=DB_USER, passwd=DB_PASS, db=DB_NAME)	 
    except:	 
        return False	 
 
def create_user(username, passwd):	 
    	 
    db = connect_db()	 
    if not db:	 
        print "Can't connect MySQL!"
        return None
 
    cursor = db.cursor()	 
 
    salt = randomValue(16)	 	 
    passwd_md5 = hashlib.md5(salt+passwd).hexdigest()	 
 
    
    try:	 
        cursor.execute("INSERT INTO users (`username`, `pass_salt`, `pass_md5`) VALUES (%s, %s, %s)", (username, salt, passwd_md5)) 
        cursor.execute("SELECT userid FROM users WHERE username=%s", (username,) ) 
        id = cursor.fetchone()
        db.commit()
        cursor.close()
        db.close()
        return id[0]	 
    except:	 
        print 'Username was already taken. Please select another'	 
        return None
 
def authenticate_user(username, passwd):	 
    db = connect_db()	 
    if not db:	 
        print "Can't connect MySQL!"
        return False
 
    cursor = db.cursor()	 
 
    cursor.execute("SELECT pass_salt, pass_md5 FROM users WHERE username=%s", (username,))

    row = cursor.fetchone()
    cursor.close()
    db.close()
    if row is None:     
        return False
    salt = row[0]
    correct_md5 = row[1]
    tried_md5 = hashlib.md5(salt+passwd).hexdigest()
    return correct_md5 == tried_md5
 
def randomValue(length):	 
    	 
    salt_chars = 'abcdefghijklmnopqrstuvwxyz0123456789'

    return ''.join(random.choice(salt_chars) for x in range(length))
 
if __name__ == '__main__':	 
    user = randomValue(10)
    passwd = randomValue(16)	 
 
    new_user_id = create_user(user, passwd)
    if new_user_id is None:
        print 'Failed to create user %s' % user
        sys.exit(1)
    auth = authenticate_user(user, passwd)	 
    if auth:	 
        print 'User %s authenticated successfully' % user	 
    else:	 
        print 'User %s failed' % user