How do I make an oscillating servo with arduino UNO?

So I have done some research and this code works, I just need to make a toggle button, when I press the button, it turns off but when we release, it constinues.
Code here:
#include <Servo.h>

Servo servo;
int angle = 10;
int switchstate = 1;
void setup() {
servo.attach(8);
servo.write(angle);
}

void loop()
{
if (switchstate = 1);
// scan from 0 to 180 degrees
for(angle = 10; angle < 180; angle++)
{
servo.write(angle);
delay(15);
}
// now scan back from 180 to 0 degrees
for(angle = 180; angle > 10; angle--)
{
servo.write(angle);
delay(15);
}
}
Board is in the attatchment. Thanks!

sweep_bb.png