If HTTP client asks for JSON, then time out the response

An HTTP response does not have to be an infinite stream, and in fact
life is simpler if it is not. The timeout in the web wrappers can
be used to close the response and return normally to a client
that has been waiting more than (say) 1s, instead of treating
it as an error condition.

Error handling is still kind of unsolved.

spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/RestApplicationTests.java

@@ -90,6 +90,14 @@ public class RestApplicationTests {
 						.getBody()).isEqualTo("foobar");
 	}
 
+	@Test
+	public void timeoutJson() throws Exception {
+		assertThat(rest
+				.exchange(RequestEntity.get(new URI("/timeout"))
+						.accept(MediaType.APPLICATION_JSON).build(), String.class)
+				.getBody()).isEqualTo("[\"foo\"]");
+	}
+
 	@Test
 	public void emptyJson() throws Exception {
 		assertThat(rest
@@ -213,6 +221,13 @@ public class RestApplicationTests {
 			return () -> Flux.fromIterable(Collections.emptyList());
 		}
 
+		@Bean
+		public Supplier<Flux<String>> timeout() {
+			return () -> Flux.create(emitter -> {
+				emitter.next("foo");
+			});
+		}
+
 		@Bean
 		public Supplier<Flux<List<String>>> sentences() {
 			return () -> Flux.just(Arrays.asList("go", "home"),