Fix comment

Author: fabianfett

Diff for: Sources/AsyncHTTPClient/ConnectionPool/HTTPRequestStateMachine.swift

@@ -207,15 +207,23 @@ struct HTTPRequestStateMachine {
 
         case .running(.streaming, .receivingBody(let responseHead, _)),
              .running(.endSent, .receivingBody(let responseHead, _)) where error as? NIOSSLError == .uncleanShutdown:
+            // This code is only reachable for request and responses, which we expect to have a body.
+            // We depend on logic from the HTTPResponseDecoder here. The decoder will emit an
+            // HTTPResponsePart.end right after the HTTPResponsePart.head, for every request with a
+            // CONNECT or HEAD method and every response with a 1xx, 204 or 304 response status.
+            //
+            // For this reason we only need to check the "content-length" or "transfer-encoding"
+            // headers here to determine if we are potentially in an EOF terminated response.
 
-            // if we have already received the response head, the parser will ensure that we receive
-            // the complete response. we can ignore this error. we might see a HTTPParserError very
-            // soon.
             if responseHead.headers.contains(name: "content-length") || responseHead.headers.contains(name: "transfer-encoding") {
+                // If we have already received the response head, the parser will ensure that we
+                // receive a complete response, if the content-length or transfer-encoding header
+                // was set. In this case we can ignore the NIOSSLError.uncleanShutdown. We will see
+                // a HTTPParserError very soon.
                 return .wait
             }
 
-            // if the response is EOF terminated, we need to rely on a clean tls shutdown to be sure
+            // If the response is EOF terminated, we need to rely on a clean tls shutdown to be sure
             // we have received all necessary bytes. For this reason we forward the uncleanShutdown
             // error to the user.
             self.state = .failed(error)