Do I Need to Close the Response Body After an HTTP GET Error in Go?

Do HTTP Errors Require Response Body Closure?

In web development, it's often necessary to handle responses from HTTP requests. The http.Get(url) function in Go is used for this purpose. However, it raises the question: is it necessary to close the response body if an error occurs during the GET request?

Error Handling Considerations

According to general programming principles, when a function returns multiple values, one of which is an error, the error should be checked first before proceeding. Non-error values should return zero values in the presence of an error.

Behavior of http.Get()

The documentation for http.Get() does not deviate from this principle. Therefore, error handling should be handled as follows:

res, err := http.Get(url)
if err != nil {
    log.Printf("Error: %s\n", err)
    return
}

defer res.Body.Close()
// Read/work with body

Special Case for Redirections

JimB confirms that when a non-nil error is returned, even if the response is non-nil, it's not necessary to close it. However, there's an exception in the case of redirection errors. The response may contain context and additional information about where the redirect failed.

Closing Non-Nil Response Body with Error

If you want to close the response body when there's a non-nil response and error, you can do so in one of these ways:

res, err := http.Get(url)
if err != nil {
    log.Printf("Error: %s\n", err)
}
if res != nil {
    defer res.Body.Close()
    // Read/work with body
}

res, err := http.Get(url)
if err != nil {
    log.Printf("Error: %s\n", err)
}
if res == nil {
    return
}

defer res.Body.Close()
// Read/work with body

Guarantee of Non-Nil Body

The documentation for http.Response guarantees that Response.Body will never be nil, even if there's no response data or the body has a zero length.

Conclusion

In conclusion, it's not necessary to close the response body in the event of an error from http.Get(), unless the error is related to a redirection. However, it's safe to close the body if the response is non-nil, using one of the approaches outlined above.

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