Go Panic: Invalid Memory Address or Nil Pointer Dereference: How to Fix Incorrect Error Handling?

Go: Panic: Runtime Error: Invalid Memory Address or Nil Pointer Dereference

When executing a Go program, you may encounter a panic with the following error message:

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x38 pc=0x26df]

This error often indicates an issue in the way your program handles memory addresses or pointers. Let's break down a possible cause:

Problem: Incorrect Error Handling

In the provided Go code, there's an issue in the getBody function when handling the response from the HTTP client:

if err != nil {
    return nil, err
}
...
if err != nil {
    return nil, err
}

The first if err != nil check occurs before accessing the response body:

if err != nil {
    return nil, err
}

res, err := client.Do(req)

However, the defer statement for closing the response body (res.Body) executes immediately, even before the error check. This could result in a premature attempt to close the body and lead to the "invalid memory address" error.

Solution:

To resolve this issue, move the error check before accessing and closing the response body:

res, err := client.Do(req)

if err != nil {
    return nil, err
}

defer res.Body.Close()

By doing so, the code correctly checks for any potential error before working with the response body, preventing the "invalid memory address" error.

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