Solution: circle STDIN

---

examples/circle-stdin/circle_stdin.go

package main

import (
    "fmt"
    "strconv"
)

func main() {
    pi := 3.14

    var radiusStr string
    fmt.Print("radius: ")
    fmt.Scan(&radiusStr)

    radius, err := strconv.ParseFloat(radiusStr, 64)
    if err == nil {
        fmt.Println(radius)
        area := pi * radius * radius
        circumference := 2 * pi * radius
        fmt.Printf("Area: %v\n", area)
        fmt.Printf("Cirumference: %v\n", circumference)
    }
}