What causes "failed to close response body: %w" in projectdiscovery/subfinder?

Check the wrapped %w cause — if it's a connection-reset, treat the response as unreliable and retry

failed to close response body

Error message

failed to close response body: %w

What it means

PugRecon closes the HTTP response body in a deferred func; if resp.Body.Close() returns an error, an Error result with this message is emitted. This is a defensive check — close errors on response bodies rarely indicate lost data, since the body was already fully consumed or discarded.

Solutions

Check the wrapped %w cause — if it's a connection-reset, treat the response as unreliable and retry
Verify the status code handling already captured the real failure earlier in the flow
If noise-only, run the source again; the error is typically transient
Avoid custom RoundTrippers that surface spurious close errors

Example fix

// before
if err := resp.Body.Close(); err != nil {
	results <- subscraping.Result{... Error: fmt.Errorf("failed to close response body: %w", err)}
}
// after
if err := resp.Body.Close(); err != nil && resp.StatusCode == http.StatusOK {
	results <- subscraping.Result{... Error: fmt.Errorf("failed to close response body: %w", err)}
}

Defensive patterns

Strategy: try-catch

Try / catch

defer func() {
	if cerr := resp.Body.Close(); cerr != nil {
		log.Printf("non-fatal close error: %v", cerr) // don't fail the run for close errors
	}
}()

Prevention

Treat close errors as non-fatal when the body was already read
Check the wrapped cause only if the status was OK and data looks suspect
Avoid custom transports that raise spurious close errors

When it happens

Trigger: The deferred resp.Body.Close() call returns non-nil after the PugRecon API POST completes — e.g. some transports/proxies report errors on close after connection resets.

Common situations: Connection torn down abruptly mid/close by proxy or server; custom HTTP transports returning close errors; usually benign noise alongside a real network issue.

Understand the failure class

Background: "API error: {status}" and "HTTP 401/403/404/429/5xx" errors: non-2xx HTTP responses explained — this error's family across 27 libraries.

Related errors

AI-assisted analysis of projectdiscovery/subfinder@7a0b91f0fa (2026-09-06). Data as JSON: /api/errors/73ba90d593c55928. Report an issue: GitHub.

Appendix: source

Thrown at pkg/subscraping/sources/pugrecon/pugrecon.go:86

		// Prepare headers
		headers := map[string]string{
			"Authorization": "Bearer " + randomApiKey,
			"Content-Type":  "application/json",
			"Accept":        "application/json",
		}

		apiURL := "https://pugrecon.com/api/v1/domains"
		s.requests++
		resp, err := session.HTTPRequest(ctx, http.MethodPost, apiURL, "", headers, bodyReader, subscraping.BasicAuth{}) // Use HTTPRequest for full header control
		if err != nil {
			results <- subscraping.Result{Source: s.Name(), Type: subscraping.Error, Error: err}
			s.errors++
			session.DiscardHTTPResponse(resp)
			return
		}
		defer func() {
			if err := resp.Body.Close(); err != nil {
				results <- subscraping.Result{Source: s.Name(), Type: subscraping.Error, Error: fmt.Errorf("failed to close response body: %w", err)}
				s.errors++
			}
		}()

		if resp.StatusCode != http.StatusOK {
			errorMsg := fmt.Sprintf("received status code %d", resp.StatusCode)
			// Attempt to read error message from body if possible
			var apiResp pugreconAPIResponse
			if json.NewDecoder(resp.Body).Decode(&apiResp) == nil && apiResp.Message != "" {
				errorMsg = fmt.Sprintf("%s: %s", errorMsg, apiResp.Message)
			}
			results <- subscraping.Result{Source: s.Name(), Type: subscraping.Error, Error: fmt.Errorf("%s", errorMsg)}
			s.errors++
			return
		}

		var response pugreconAPIResponse
		err = json.NewDecoder(resp.Body).Decode(&response)

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