fixup: add group example

Author: not-matthias

example/fib_test.go

@@ -21,7 +21,13 @@ func BenchmarkFibonacci20(b *testing.B) {
 }
 
 func BenchmarkFibonacci30(b *testing.B) {
-	for i := 0; i < b.N; i++ {
-		fibonacci(30)
-	}
+	b.Run("fibonacci(30)", func(b *testing.B) {
+		b.Run("fibonacci(30)", func(b *testing.B) {
+			b.Run("fibonacci(30)", func(b *testing.B) {
+				for i := 0; i < b.N; i++ {
+					fibonacci(30)
+				}
+			})
+		})
+	})
 }