ensure config file is closed in PopulateConfig

[mateeaaa]

Summary

This PR resolves an unclosed file descriptor resource leak in ApiServer.PopulateConfig by ensuring that configuration files opened via os.Open are properly closed after decoding.

Root Cause Analysis

In api.go, the PopulateConfig method opens a JSON configuration file to populate proxies during server startup or reload.

While PopulateJson consumes the passed io.Reader via json.NewDecoder(data).Decode(...), it does not take ownership of closing the underlying stream. As a result, the *os.File handle allocated by os.Open(filename) remains open indefinitely for the lifetime of the process.

Solution

Add defer file.Close() immediately following the successful os.Open error check. This guarantees that the file descriptor is released back to the OS regardless of whether JSON decoding succeeds or fails.

Changes Made

• Modified api.go in PopulateConfig: added defer file.Close() right after the initial error check.