Correctly handle HEAD requests (#129)

src/service/future.rs

@@ -6,7 +6,8 @@ use crate::{
 };
 use bytes::Bytes;
 use futures_util::ready;
-use http::{Request, Response};
+use http::{Method, Request, Response};
+use http_body::Empty;
 use pin_project_lite::pin_project;
 use std::{
     future::Future,
@@ -85,6 +86,7 @@ pin_project! {
     {
         #[pin]
         pub(super) inner: crate::routing::future::RouteFuture<S, F, B>,
+        pub(super) req_method: Method,
     }
 }
 
@@ -96,6 +98,13 @@ where
     type Output = Result<Response<BoxBody>, S::Error>;
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        self.project().inner.poll(cx)
+        let this = self.project();
+        let response = futures_util::ready!(this.inner.poll(cx))?;
+        if this.req_method == &Method::HEAD {
+            let response = response.map(|_| box_body(Empty::new()));
+            Poll::Ready(Ok(response))
+        } else {
+            Poll::Ready(Ok(response))
+        }
     }
 }