go/src/encoding/gob/example_interface_test.go

type Point …

func (p Point) Hypotenuse() float64 { … }

type Pythagoras …

// This example shows how to encode an interface value. The key
// distinction from regular types is to register the concrete type that
// implements the interface.
func Example_interface() { … }

// interfaceEncode encodes the interface value into the encoder.
func interfaceEncode(enc *gob.Encoder, p Pythagoras) { … }

// interfaceDecode decodes the next interface value from the stream and returns it.
func interfaceDecode(dec *gob.Decoder) Pythagoras { … }