Why does json.Unmarshal work with reference but not pointer?

Question

This example from the json.Unmarshal docs (slightly modified for simplicity to use Animal instead of []Animal) works, no errors:

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Answer 1

I had a similiar condition before but in a different case. It is related with concept of interface in Go. If a function declares a interface as argument or return value, the caller have to pass or return the reference

In your case, json.Unmarshal accept interface as second argument