package main

import (
  "fmt"
  "os"
)

func getUsers() map[string]string {

  return map[string]string{
    "305": "Sue",
    "204": "Bob",
    "631": "Jake",
    "073": "Tracy",
  }

}

func getUser(id string) (string, bool) {

  users := getUsers()
  user, exists := users[id]
  return user, exists

}

func main() {

  if len(os.Args) != 2 {
    fmt.Println("User ID not passed")
    os.Exit(1)
  }

  userID := os.Args[1]
  name, exists := getUser(userID)

  if !exists {
    fmt.Printf("Passed user ID (%v) not found.\nUsers: \n", userID)
    for key, value := range getUsers() {
      fmt.Println("   ID:", key, "Name:", value)
    }
    os.Exit(1)
  }

  fmt.Println("Name:", name)

}