Make sure to check if headers already have a HOST value before setting

awc/src/ws.rs

@@ -233,7 +233,9 @@ impl WebsocketsRequest {
             return Either::A(err(InvalidUrl::UnknownScheme.into()));
         }
 
+        if !self.head.headers.contains_key(header::HOST) {
             self.head.headers.insert(header::HOST, HeaderValue::from_str(uri.host().unwrap()).unwrap());
+        }
 
         // set cookies
         if let Some(ref mut jar) = self.cookies {