examples: add a simple coroutine example

examples/coroutines/simple_coroutines.v

@@ -0,0 +1,37 @@
+// Build with
+// v -use-coroutines simple_coroutines.v
+//
+import coroutines
+import time
+
+fn foo(a int) {
+	for {
+		println('hello from foo() a=${a}')
+		coroutines.sleep(1 * time.second)
+	}
+}
+
+fn foo2(a int) {
+	for {
+		println('hello from foo2() a=${a}')
+		coroutines.sleep(2 * time.second)
+	}
+}
+
+fn foo3(a int) {
+	for {
+		println('hello from foo3() a=${a}')
+		coroutines.sleep(3 * time.second)
+	}
+}
+
+fn main() {
+	go foo(10)
+	go foo2(20)
+	go foo3(30)
+	for {
+		println('hello from MAIN')
+		coroutines.sleep(1 * time.second)
+	}
+	println('done')
+}