fc=30;
        g=[1 1 0 1 0 0 1 1 1 0]; %modulante
        n=1;
    while n<=length(g)
        if g(n)==0
            tx=(n-1)*0.1:0.1/100:n*0.1;
            p=(1)*sin(2*pi*fc*tx);
            plot(tx,p,'LineWidth',1.5);grid on;
            hold on;
        else 
            t=(n-1)*0.1:0.1/100:n*0.1;
            p=(2)*sin(2*pi*fc*t);
            plot(tx,p,'LineWidth',1.5);grid on;
            hold on;
        end
            n=n+1;
            
    end

This is my code for ASK modulation.
Does any have idea about the demodulation?

Someone told me that using xcorr, is it true?
another one told me t compare the modulated waveform with a normal sine wave, to see whether
the amplitudes are the same or not.

If the amplitude is the same, therefore a Binary 0 is presented; if the amplitudes are
different, a Binary 1 is presented.