refactor: move client I/O into a separate function

src/client/mod.rs

@@ -85,7 +85,7 @@ impl Client {
     /// - [`std::io::Error`] is returned in nearly all cases:
     ///   could not open a TCP connection, perform a TLS handshake,
     ///   write to or read from the TCP stream.
-    ///   Check the inner error if you need to determine what exactly happened
+    ///   Check the inner error if you need to determine what exactly happened.
     /// - [`LibError::StatusOutOfRange`] means that a server returned an incorrect status code
     ///   (less than 10 or greater than 69).
     /// - [`LibError::DataNotUtf8`] is returned when metadata (the text after a status code)
@@ -100,9 +100,12 @@ impl Client {
             .map_err(|_| InvalidUrl::ConvertError)?
             .to_owned();
 
+        // TCP connection
         let stream = self.try_connect(host, port).await?;
-        let mut stream = self.connector.connect(domain, stream).await?;
+        // TLS connection via tokio-rustls
+        let stream = self.connector.connect(domain, stream).await?;
 
+        // certificate verification
         if let Some(ssv) = &self.ss_verifier {
             let cert = stream
                 .get_ref()
@@ -117,6 +120,14 @@ impl Client {
             }
         }
 
+        self.perform_io(url_str, stream).await
+    }
+
+    pub(crate) async fn perform_io<IO: AsyncReadExt + AsyncWriteExt + Unpin>(
+        &self,
+        url_str: &str,
+        mut stream: IO,
+    ) -> Result<Response<BufReader<IO>>, LibError> {
         // Write URL, then CRLF
         stream.write_all(url_str.as_bytes()).await?;
         stream.write_all(b"\r\n").await?;