Explain how encoding/json marshaling works with struct tags and custom marshalers.

encoding/json uses struct tags to control JSON field names and behavior. Implement json.Marshaler and json.Unmarshaler interfaces for custom serialization logic.

Struct tags and custom marshalers

Common pitfalls

1
Unexported fields are silently ignored — always export fields you want serialized
2
interface{} numbers unmarshal as float64 by default — use UseNumber() for large integers
3
omitempty omits zero values: 0, false, "", nil — careful with intentional zero values
4
Anonymous embedded structs promote their fields to the parent — useful but can cause field collisions
5
json.RawMessage allows deferring or passing through raw JSON without parsing