avoid using interface with only 1 concrete type

interface_1_concrete.go

package main

import (
	"fmt"
	"time"
)

type Shape interface {
	Area() float64
}

type Circle struct {
	radius float64
}

func (c *Circle) Area() float64 {
	return 3.14 * c.radius * c.radius
}

func main() {
	// Use the Shape interface
	start := time.Now()
	var s Shape = &Circle{radius: 10}
	for i := 0; i < 100000; i++ {
		s.Area()
	}
	elapsed := time.Since(start)
	fmt.Printf("Using Shape interface: %s\n", elapsed) // Using Shape interface: 358µs

	// Use the Circle type directly
	start = time.Now()
	c := Circle{radius: 10}
	for i := 0; i < 100000; i++ {
		c.Area()
	}
	elapsed = time.Since(start)
	fmt.Printf("Using Circle type directly: %s\n", elapsed) // Using Circle type directly: 341.917µs
}