How to Resolve 'invalid memory address or nil pointer dereference' Errors When Mapping Structs in Go?

Debugging "invalid memory address or nil pointer dereference" Error in Mapping Operations

When accessing struct fields within a map, one may encounter the "invalid memory address or nil pointer dereference" error. This issue typically arises when attempting to dereference a nil pointer.

In the specific example provided:

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

The map condition is initialized as an empty map of pointers to *guardduty.Condition structs. As a result, accessing condition["id"] without first initializing it will return a nil value, which cannot be dereferenced to set the Equals field.

To resolve this issue, you can first check if the key exists in the map using the following approach:

if cond, 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 performing this check, you can ensure that the pointer is not nil before attempting to dereference it and set the Equals field.

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