How to Prevent 'runtime error: invalid memory address or nil pointer dereference' in a Go Web Crawler?

Invalid Memory Address or Nil Pointer Dereference in Webcrawler

While developing a webcrawler in Go, users may encounter the error "runtime error: invalid memory address or nil pointer dereference." This error stems from incorrect memory handling or accessing nil pointers.

In the provided code, the issue arises in the advancedFetcher and basicFetcher functions. Within basicFetcher, the error is likely caused by directly using http.Get, which doesn't allow for graceful error handling. If http.Get returns an error, resp.Body will be nil, leading to an attempt to close a nil pointer in resp.Body.Close().

To resolve this, the functions should be rewritten to return a (result, error) pair. This allows for proper error handling and termination before encountering nil pointers. For example, instead of using http.Get, one can use client.Get, which returns a (resp *http.Response, err error) pair.

In the main function, when iterating over the rows slice, the code should check for errors returned by advancedFetcher and basicFetcher. If an error is encountered, the program should handle it gracefully rather than allowing it to bubble up and cause the panic.

By incorporating proper error handling and returning (result, error) pairs, the code will be more robust and handle potential errors gracefully, preventing the "runtime error: invalid memory address or nil pointer dereference" error.

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