Fix config options merging

Author: moogle19

lib/thousand_island/transports/ssl.ex

@@ -57,7 +57,10 @@ defmodule ThousandIsland.Transports.SSL do
       reuseaddr: true
     ]
 
-    resolved_options = @hardcoded_options ++ user_options ++ default_options
+    resolved_options =
+      default_options
+      |> Keyword.merge(user_options)
+      |> Keyword.merge(@hardcoded_options)
 
     if not Enum.any?(
          [:keyfile, :key, :sni_hosts, :sni_fun],

lib/thousand_island/transports/tcp.ex

@@ -55,7 +55,11 @@ defmodule ThousandIsland.Transports.TCP do
       reuseaddr: true
     ]
 
-    resolved_options = @hardcoded_options ++ user_options ++ default_options
+    resolved_options =
+      default_options
+      |> Keyword.merge(user_options)
+      |> Keyword.merge(@hardcoded_options)
+
     :gen_tcp.listen(port, resolved_options)
   end