good good study, day day up!

vendor/gopl.io/ch8/spinner/main.go

@@ -0,0 +1,38 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 218.
+
+// Spinner displays an animation while computing the 45th Fibonacci number.
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+//!+
+func main() {
+	go spinner(100 * time.Millisecond)
+	const n = 45
+	fibN := fib(n) // slow
+	fmt.Printf("\rFibonacci(%d) = %d\n", n, fibN)
+}
+
+func spinner(delay time.Duration) {
+	for {
+		for _, r := range `-\|/` {
+			fmt.Printf("\r%c", r)
+			time.Sleep(delay)
+		}
+	}
+}
+
+func fib(x int) int {
+	if x < 2 {
+		return x
+	}
+	return fib(x-1) + fib(x-2)
+}
+
+//!-