Go example: hello world and fibonacci

Run a Go program that prints Hello World and computes Fibonacci numbers.

A minimal Go program with package main and a func main() entry point. It prints a greeting with fmt.Println, then loops from 0 to 9 and uses fmt.Printf to print each Fibonacci number. The fib function is a classic recursive implementation that returns n for the base case and otherwise sums fib(n-1) and fib(n-2).