Stop looking for user input with 'bufio.NewReader(os.Stdin)' - go

Question

New to golang and programming in general. I am currently writing a small quiz program for a learning task and ran into a snag that the tutorial does not address because I have features not included on the tutorial.
Code is included below:
func runQuestions(randomize bool) int {
tempqSlice := qSlice //Create temporary set of questions (Don't touch original)
if randomize { //If user has chosen to randomize the question order
tempqSlice = shuffle(tempqSlice) //Randomize
}
var runningscore int
userinputchan := make(chan string) //Create return channel for user input
go getInput(userinputchan) //Constantly wait for user input
for num, question := range tempqSlice { //Iterate over each question
fmt.Printf("Question %v:\t%v\n\t", num+1, question.GetQuestion())
select {
case <-time.After(5 * time.Second): //
fmt.Println("-time up! next question-")
continue
case input := <-userinputchan:
if question.GetAnswer() == input { //If the answer is correct
runningscore++
continue //Continue to next question
}
}
}
return runningscore
}
func getInput(returnchan chan<- string) {
for {
reader := bufio.NewReader(os.Stdin) //Create reader
input, _ := reader.ReadString('\n') //Read from
returnchan <- strings.TrimSpace(input) //Trim the input and send it
}
}
Because the specification of the problem requires each question to have a timelimit, I have set a 'endless for loop go routine' running that waits for user input and then sends it when it is given. My problem is simple: I would like to stop the reader looking for input once the quiz is over but since the 'reader.ReadString('/n')' is already awaiting input, I'm not sure how.

Answer 1

I would like to stop the reader looking for input once the quiz is over
While the reader is looking for input, you can use a goroutine that runs in its background to check whether the quiz timer is expired.
Suppose your timer for quiz is 30 seconds. Pass the timer to the goroutine getInputand check for the timer expiry.
var runningscore int
userinputchan := make(chan string) //Create return channel for user input
myTime := flag.Int("timer", 30, "time to complete the quiz")
timer := startTimer(myTime)
go getInput(userinputchan, timer)
func startTimer(myTime *int) *time.Timer {
return time.NewTimer(time.Duration(*myTime) * time.Second)
}
func getInput(returnchan chan<- string, timer *time.Timer) {
for {
reader := bufio.NewReader(os.Stdin) //Create reader
go checkTime(timer)
input, _ := reader.ReadString('\n') //Read from
returnchan <- strings.TrimSpace(input) //Trim the input and send it
}
}
func checkTime(timer *time.Timer) {
<-timer.C
fmt.Println("\nYour quiz is over!!!")
// print the final score
os.Exit(1)
}

Answer 2

You cannot do this out of the box, however you can make a workaround by reading character by character from stdin, buffering the inputs and only sending the buffered data when the user hits Enter.
Unfortunately, there is there is no standard package for reading character by character, I will be using github.com/eiannone/keyboard. (You can get it by go get -u github.com/eiannone/keyboard).
The following class will be your input system. You can instantiate it by calling NewInput(yourResultChannel). This will start reading from stdin character by character and buffers them into buf. Once Enter (char == 0) is hit, it sends the contents of the buffer to the resultChannel end resets the buffer.
type Input struct {
lock sync.Mutex
buf []rune
resultCh chan string
}
func NewInput(resultCh chan string) *Input {
i := &Input{
resultCh: resultCh,
}
go i.readStdin()
return i
}
func (i *Input) ResetBuffer() {
i.lock.Lock()
defer i.lock.Unlock()
i.resetBuffer()
}
func (i *Input) readStdin() {
for {
char, _, err := keyboard.GetSingleKey()
if err != nil {
panic(err)
}
fmt.Printf("%s", string(char))
i.lock.Lock()
if char == 0 {
i.resultCh <- strings.TrimSpace(string(i.buf))
i.resetBuffer()
} else {
i.buf = append(i.buf, char)
}
i.lock.Unlock()
}
}
func (i *Input) resetBuffer() {
i.buf = []rune{}
}
Your only remaining job is to create an instance of the Input class at the point where you were previously starting your getInput() goroutine.
userinputchan := make(chan string) //Create return channel for user input
input := NewInput(userinputchan)
and reset the buffer when the question times out so that the previous garbage input won't be part of the new question's answer. In the select statement:
case <-time.After(5 * time.Second):
fmt.Println("-time up! next question-")
input.ResetBuffer()
continue
Full code: https://play.golang.org/p/-IXVvY9dOZO