send Connection.Close-ok before closing socket

Do that by dropping the write_loop fiber

src/amqproxy/client.cr

@@ -9,7 +9,7 @@ module AMQProxy
     Log = ::Log.for(self)
     getter credentials : Credentials
     @channel_map = Hash(UInt16, UpstreamChannel?).new
-    @outgoing_frames = Channel(AMQ::Protocol::Frame).new(128)
+    @lock = Mutex.new
     @frame_max : UInt32
     @channel_max : UInt16
     @heartbeat : UInt16
@@ -21,7 +21,6 @@ module AMQProxy
       @frame_max = tune_ok.frame_max
       @channel_max = tune_ok.channel_max
       @heartbeat = tune_ok.heartbeat
-      spawn write_loop
     end
 
     # Keep a buffer of publish frames
@@ -125,36 +124,27 @@ module AMQProxy
     else
       Log.debug { "Disconnected" }
     ensure
-      @outgoing_frames.close
       socket.close rescue nil
       close_all_upstream_channels
     end
 
-    private def write_loop(socket = @socket)
-      while frame = @outgoing_frames.receive?
-        socket.write_bytes frame, IO::ByteFormat::NetworkEndian
-        socket.flush unless expect_more_publish_frames?(frame)
-        case frame
-        when AMQ::Protocol::Frame::Channel::Close
-          @channel_map[frame.channel] = nil
-        when AMQ::Protocol::Frame::Channel::CloseOk
-          @channel_map.delete(frame.channel)
-        when AMQ::Protocol::Frame::Connection::CloseOk
-          break
-        end
+    # Send frame to client, channel id should already be remapped by the caller
+    def write(frame : AMQ::Protocol::Frame)
+      @lock.synchronize do
+        @socket.write_bytes frame, IO::ByteFormat::NetworkEndian
+        @socket.flush unless expect_more_publish_frames?(frame)
+      end
+      case frame
+      when AMQ::Protocol::Frame::Channel::Close
+        @channel_map[frame.channel] = nil
+      when AMQ::Protocol::Frame::Channel::CloseOk
+        @channel_map.delete(frame.channel)
+      when AMQ::Protocol::Frame::Connection::CloseOk
+        @socket.close rescue nil
       end
     rescue ex : IO::Error
       # Client closed connection, suppress error
-    ensure
-      @outgoing_frames.close
-      socket.close rescue nil
-    end
-
-    # Send frame to client, channel id should already be remapped by the caller
-    def write(frame : AMQ::Protocol::Frame)
-      @outgoing_frames.send frame
-    rescue Channel::ClosedError
-      # do nothing
+      @socket.close rescue nil
     end
 
     def close_connection(code, text, frame = nil)
@@ -196,9 +186,8 @@ module AMQProxy
       # @socket.read_timeout = 1.seconds
     end
 
-    # Close the outgoing frames channel which will let write_loop close the socket
     def close_socket
-      @outgoing_frames.close
+      @socket.close rescue nil
     end
 
     private def set_socket_options(socket = @socket)