fix FileNotFoundException when response code is 4xx or 5xx

tools/goctl/api/ktgen/gen.go

@@ -36,7 +36,10 @@ suspend fun apiRequest(
     val url = URL(SERVER + uri)
     with(url.openConnection() as HttpURLConnection) {
         requestMethod = method
-        headerFields["Content-Type"] = listOf("Application/json")
+        doInput = true
+        if (method == "POST" || method == "PUT") {
+            setRequestProperty("Content-Type", "application/json")
+            doOutput = true
             val data = when (body) {
                 is String -> {
                     body
@@ -48,15 +51,18 @@ suspend fun apiRequest(
             val wr = OutputStreamWriter(outputStream)
             wr.write(data)
             wr.flush()
-
+        }
+        if (responseCode >= 400) {
+            BufferedReader(InputStreamReader(errorStream)).use {
+                val response = it.readText()
+                onFail?.invoke(response)
+            }
+            return@with
+        }
         //response
         BufferedReader(InputStreamReader(inputStream)).use {
             val response = it.readText()
-            if (responseCode == 200) {
             onOk?.invoke(response)
-            } else {
-                onFail?.invoke(response)
-            }
         }
     }
     eventually?.invoke()