docs: fix channel select example (#10213)

doc/docs.md

@@ -2885,29 +2885,48 @@ y := <-ch2 ?
 The `select` command allows monitoring several channels at the same time
 without noticeable CPU load.  It consists of a list of possible transfers and associated branches
 of statements - similar to the [match](#match) command:
-```v wip
+```v
 import time
-fn main () {
-  c := chan f64{}
+
+fn main() {
 	ch := chan f64{}
 	ch2 := chan f64{}
 	ch3 := chan f64{}
 	mut b := 0.0
-  // ...
+	c := 1.0
+	// ... setup go threads that will send on ch/ch2
+	go fn (the_channel chan f64) {
+		time.sleep(5 * time.millisecond)
+		the_channel <- 1.0
+	}(ch)
+	go fn (the_channel chan f64) {
+		time.sleep(1 * time.millisecond)
+		the_channel <- 1.0
+	}(ch2)
+	go fn (the_channel chan f64) {
+		_ := <-the_channel
+	}(ch3)
+	//
 	select {
 		a := <-ch {
 			// do something with `a`
+			eprintln('> a: $a')
 		}
 		b = <-ch2 {
 			// do something with predeclared variable `b`
+			eprintln('> b: $b')
 		}
 		ch3 <- c {
 			// do something if `c` was sent
+			time.sleep(5 * time.millisecond)
+			eprintln('> c: $c was send on channel ch3')
 		}
 		> 500 * time.millisecond {
 			// do something if no channel has become ready within 0.5s
+			eprintln('> more than 0.5s passed without a channel being ready')
 		}
 	}
+	eprintln('> done')
 }
 ```