Ubuntu 20 how to increase swapfile

After installing server, I increased RAM, but swap file remains the same, so I have to increase itrmanually. I increased RAM from $ to 8 GB so I have to increase swap file accordingly. In Ubuntu 20.04 swapfile out of the box is called swap.img not swapfile, so the commands will be as follows: 

• type sudo su so you don't have to type sudo before each command

ubuntu@grayflow:~$ sudo su

[sudo] password for ubuntu:

• check swap size and name

root@grayflow:/home/ubuntu# swapon --show

NAME      TYPE SIZE USED PRIO

/swap.img file   4G 2.1G   -2

• turn off swap

root@grayflow:/home/ubuntu# swapoff -a

• increase swap file

root@grayflow:/home/ubuntu# dd if=/dev/zero of=/swap.img bs=1M count=8192

8192+0 records in

8192+0 records out

8589934592 bytes (8.6 GB, 8.0 GiB) copied, 131.193 s, 65.5 MB/s

• turn on swapping

root@grayflow:/home/ubuntu# mkswap /swap.img

Setting up swapspace version 1, size = 8 GiB (8589930496 bytes)

no label, UUID=a1dfcfc3-577d-4ed2-b706-f7c8eeeec69f

root@grayflow:/home/ubuntu# swapon /swap.img

root@grayflow:/home/ubuntu# swapon -s

Filename                                Type            Size    Used    Priority

/swap.img                               file            8388604 780     -2