How Can I Deep Copy Data Structures in Go?

Deep Copying Data Structures in Go: Is It Possible?

In Go, creating a deep copy of a data structure means duplicate its contents, including any nested structures or pointers. Unlike some other programming languages, Go does not provide built-in deep copying functionality.

To address this, third-party libraries like gods have been developed. However, as you've encountered, using these libraries for deep copying may not always produce the desired results.

Unfortunately, in Go, it's generally not possible to fully deep copy a data structure instance without modifying its code. This limitation stems from the fact that there is no built-in "copy constructor" mechanism, and reflection (which allows reading unexported fields) cannot be used to set them.

Even unsafe operations, as provided by the unsafe package, should be avoided due to their unpredictable behavior across different Go releases and platforms.

As mentioned in your example with a hash set, the gods library does not fully copy the contents of the data structure. This is expected as it cannot deep copy unexported values.

In cases where you need to deep copy data structures, the recommended approach is to use the idiomatic Go pattern of implementing the deepcopy function within the specific data structure package itself. This allows the package authors to handle deep copying in a manner that is tailored to the specific data structure implementation.

As an alternative, you could consider using a serialization/deserialization approach. This involves converting the data structure to a stream of bytes (serialization) and then reconstituting it from the stream (deserialization). While this achieves a form of deep copying, it may not be suitable for all scenarios due to the performance overhead and potential data loss if the data structure contains complex or circular references.

Remember, the lack of a built-in deep copying mechanism does not render such functionality impossible in Go. It simply requires a more hands-on approach or reliance on specific libraries that provide such functionality for the data structures you require.

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