.go

package main

import (
	"fmt"
	"math"
	"os"
	"time"

	"github.com/faiface/beep"
	"github.com/faiface/beep/effects"
	"github.com/faiface/beep/speaker"
	"github.com/faiface/beep/wav"
)

func main() {
	beep.SampleRate = 44100
	speaker.Init(time.Second / 60)

	f, _ := os.Open("13 Face to Face.wav")
	s, _ := wav.Decode(f)
	v := &effects.Volume{
		Streamer: s,
		Base:     math.Phi,
		Volume:   0.0,
	}

	speaker.Play(v)

	for {
		var volume float64
		fmt.Scan(&volume)
		speaker.Lock()
		v.Volume = volume
		speaker.Unlock()

		const (
			sliderLen = 16
			volumeMin = -8
			volumeMax = 0
		)
		dots := int(sliderLen * (volume - volumeMin) / (volumeMax - volumeMin))
		fmt.Print("[")
		for i := 0; i < dots; i++ {
			fmt.Print("#")
		}
		for i := dots; i < sliderLen; i++ {
			fmt.Print(" ")
		}
		fmt.Println("]")
	}
}