Writing a Typing Speed Test CLI Application in Golang

package main

import (
    "bufio"
    "fmt"
    "log"
    "math/rand"
    "os"
    "strings"
    "time"
)

var sentences = []string{
    "There are 60 minutes in an hour, 24 hours in a day and 7 days in a week",
    "Nelson Mandela is one of the most renowned freedom fighters Africa has ever produced",
    "Nigeria is the most populous black nation in the world",
    "Peter Jackson's Lord of the rings is the greatest film of all time",
}

// A generic helper function that randomly selects an item from a slice
func Choice[T any](ts []T) T {
    return ts[rand.Intn(len(ts))]
}

// Prompts and collects user input from the terminal
func Input(prompt string) (string, error) {
    fmt.Print(prompt)
    r := bufio.NewReader(os.Stdin)

    line, err := r.ReadString('\n')
    if err != nil {
        return "", err
    }

    return strings.Trim(line, "\n\r\t"), nil
}

// Compares two strings and keeps track of the characters  
// that match and those that don't
func CompareChars(target, source string) (int, int) {
    var valid, invalid int

    // typed some of the words
        // resize target to length of source
    if len(target) > len(source) {
        diff := len(target) - len(source)
        invalid += diff
        target = target[:len(source)]
    }

    // typed more words than required
        // resize source to length of target
    if len(target) < len(source) {
        invalid++
        source = source[:len(target)]
    }

    for i := 0; i < len(target); i++ {
        if target[i] == source[i] {
            valid++
        }
        if target[i] != source[i] {
            invalid++
        }
    }

    return valid, invalid
}

// Calculates the degree of correctness
func precision(pos, fal int) int {
    return pos / (pos + fal) * 100
}

// Self explanatory - don't stress me ?
func timeElapsed(start, end time.Time) float64 {
    return end.Sub(start).Seconds()
}

// Refer to the last comment
func accuracy(correct, total int) int {
    return (correct / total) * 100
}

// ?
func Speed(chars int, secs float64) float64 {
    return (float64(chars) / secs) * 12
}

func main() {
    fmt.Println("Welcome to Go-Speed")
    fmt.Println("-------------------")

    for {
        fmt.Printf("\nWould you like to continue? (y/N)\n\n")
        choice, err := Input(">> ")
        if err != nil {
            log.Fatalf("could not read value: %v", err)
        }

        if choice == "y" {
            fmt.Println("Starting Game...")
            timer := time.NewTimer(time.Second)
            fmt.Print("\nBEGIN TYPING NOW!!!\n\n")
            _ = <-timer.C

            sentence := Choice(sentences)
            fmt.Printf("%s\n", sentence)

            start := time.Now()
            response, err := Input(">> ")
            if err != nil {
                log.Fatalf("could not read value: %v", err)
            }

            elasped := timeElapsed(start, time.Now())
            valid, invalid := CompareChars(sentence, response)
            fmt.Print("\nResult!\n")
            fmt.Println("-------")
            fmt.Printf("Correct Characters: %d\nIncorrect Characters: %d\n", valid, invalid)
            fmt.Printf("Accuracy: %d%%\n", accuracy(valid, len(sentence)))
            fmt.Printf("Precision: %d%%\n", precision(valid, invalid))
            fmt.Printf("Speed: %.1fwpm\n", Speed(len(sentence), elasped))
            fmt.Printf("Time Elasped: %.2fsec\n", elasped)
        }

        if choice == "N" {
            fmt.Println("Quiting Game...")
            break
        }

        if choice != "N" && choice != "y" {
            fmt.Println("Invalid Option")
        }
    }
}