Add rust example

rust_fib/src/main.rs

@@ -0,0 +1,18 @@
+
+use std::io;
+
+fn fib(n: i64) -> i64 {
+    match n {
+        0 => 1,
+        1 => 1,
+        o => fib(o-1) + fib(o-2),
+    }
+}
+
+fn main() {
+    println!("enter number to fib:");
+    let mut buffer = String::new();
+    let stdin = io::stdin();
+    stdin.read_line(&mut buffer).unwrap();
+    println!("{}", fib(buffer.trim().parse::<i64>().unwrap()));
+}