Ambiguous struct embedding resolution

distance.go

package main

import (
	"fmt"
	"os"
	"strconv"
)

type Cycle struct{}

func (g *Cycle) time(distance float64) float64 {
	// using speed = distance / time
	return 60 * distance / 15
}

type Walk struct{}

func (g *Walk) time(distance float64) float64 {
	// using speed = distance / time
	return 60 * distance / 5
}

// CycleAndWalk half walking, half cycling
type CycleAndWalk struct {
	Cycle
	Walk
}

func (g *CycleAndWalk) time(distance float64) float64 {
	cycling := g.Cycle.time(distance) / 2
	walking := g.Walk.time(distance) / 2
	return walking + cycling
}

func main() {
	if len(os.Args) < 2 {
		fmt.Println("usage: travel n.n (where n.n is the distance in km such as 3.4)")
		os.Exit(0)
	}

	distance, err := strconv.ParseFloat(os.Args[1], 64)
	if err != nil {
		fmt.Printf("can't calculate distance of %s", os.Args[1])
		os.Exit(0)
	}

	c := &Cycle{}
	fmt.Printf("Cycling %.2fkm would take %.2f minutes\n", distance, c.time(distance))

	w := &Walk{}
	fmt.Printf("Walking %.2fkm would take %.2f minutes\n", distance, w.time(distance))

	cw := &CycleAndWalk{}
	fmt.Printf("Cycling %.2fkm then walking %.2fkm would take %.2f minutes\n", distance/2, distance/2, cw.time(distance))

}