How do I detect input from the user while a bash script is in execution?

Question

While my code reads and displays lines from a file I want to detect if j or k keys are pressed. This will increase or decrease the rate at which the words are displayed to the screen.

I am not sure how to go about this. I did a bit of research and the only thing I found was using the read command to listen for input from a user but how would I have the read command always listening while the script is in execution?

I also found a trap command but I think that is only to end the program? I use the trap command to exit when ctrl-c is pressed. Is it possible to use the trap command to listen for j or k keys as well?

any suggestions would be appreciated

atm I have this piece of code but it doesn't work the way I need it to. The script usage is: script file.txt [speed]

#!/bin/bash
trap end INT
file=$1
wpm=$2
input=$2

filecheck() {
  #some code
}

initialspeed() {
   #some code
}

fileread() {
  #some code
}

display() {
   #some code
}

end() {
   #some code
}

#INCREASE OR DECREASE WPM SPEED
jk() {
input=$2
        read -s -n 1 key
        if [ "$key" == "k" ]
        then
                echo K HIT
                exit
                input=$input+10
                wpm=$(bc <<< "scale=2;60/$input")
                        if [ "$input" -gt 1000 ]
                        then
                                wpm=0.06
                        fi
        fi

        if [ "$key" == "j" ]
        then
                echo J HIT
                input=$input-10
                wpm=$(bc <<< "scale=2;60/$input")
                        if [ "$input" -lt 100 ]
                        then
                                wpm=0.6
                        fi
        fi
}

#CALL FUNCTIONS
echo
filecheck
initialspeed
fileread
jk #IM not sure where to call this function to make it listen all the time
display

EDIT: This is not a duplicate question because my problem isn't that I need to read input without waiting for the enter key to be pressed. I need to detect input at ANY point in the script execution. I already use -n 1 to read only 1 key press