tests: handle errors properly in examples (#748)

tokio-signal/examples/multiple.rs

@@ -11,7 +11,7 @@ mod platform {
     use futures::{Future, Stream};
     use tokio_signal::unix::{Signal, SIGINT, SIGTERM};
 
-    pub fn main() {
+    pub fn main() -> Result<(), Box<::std::error::Error>> {
         // Create a stream for each of the signals we'd like to handle.
         let sigint = Signal::new(SIGINT).flatten_stream();
         let sigterm = Signal::new(SIGTERM).flatten_stream();
@@ -27,26 +27,26 @@ mod platform {
          (i.e. this binary)"
         );
         let (item, _rest) = ::tokio::runtime::current_thread::block_on_all(stream.into_future())
-            .ok()
-            .unwrap();
+            .map_err(|_| "failed to wait for signals")?;
 
         // Figure out which signal we received
-        let item = item.unwrap();
+        let item = item.ok_or("received no signal")?;
         if item == SIGINT {
             println!("received SIGINT");
         } else {
             assert_eq!(item, SIGTERM);
             println!("received SIGTERM");
         }
+        Ok(())
     }
 
 }
 
 #[cfg(not(unix))]
 mod platform {
-    pub fn main() {}
+    pub fn main() -> Result<(), Box<::std::error::Error>> {Ok(())}
 }
 
-fn main() {
+fn main() -> Result<(), Box<std::error::Error>> {
     platform::main()
 }