How to Handle 'invalid memory address or nil pointer dereference' Errors When Accessing Map Fields in Go?

Map Access Error: "invalid memory address or nil pointer dereference"

Problem:

When attempting to access a struct field from a map, an error occurs indicating an invalid memory address or nil pointer dereference. This error arises specifically on the line where a slice of pointers (*string) is assigned to a field in a guardduty.Condition struct.

Code:

condition := map[string]*guardduty.Condition{}
condition["id"].Equals = strPtr

Error:

invalid memory address or nil pointer dereference
gdreport/main.go:30 +0x1e6

Explanation:

The error stems from the fact that the condition map is initially an empty map of pointers. When accessing the "id" key, you are effectively attempting to retrieve a nil value of *guardduty.Condition. This explains the error, as accessing the Equals field of a nil pointer is invalid.

Solution:

To resolve this issue, you must first check if the "id" key exists in the condition map. If it does not, you can initialize a new guardduty.Condition and assign it to the "id" key.

Updated Code:

if _, ok := condition["id"]; !ok { // <nil> false
    log.Println("Pointer is null")
} else {
    // Init new guardduty.Condition
    // and assign to required key
    nc := &guardduty.Condition{Equals: strPtr}
    condition["id"] = nc
}

By checking for the existence of the key first, you can avoid attempting to access a nil pointer, ensuring that the code executes as intended.

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