Getting error while installing using APT repository.

[tehsunnliu]

Hello,
I'm trying to install GoCD on Ubuntu using the APT repository following the instructions here
However, I'm getting the following error

sudo apt-get update
deb [signed-by=/etc/apt/keyrings/gocd.gpg] https://download.gocd.org /
Hit:1 https://dl.google.com/linux/chrome/deb stable InRelease
Get:2 https://download.gocd.org  InRelease [2478 B]                                                                   
Err:2 https://download.gocd.org  InRelease                                                                            
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY D8843F288816C449
Hit:3 http://security.ubuntu.com/ubuntu jammy-security InRelease
Hit:4 http://in.archive.ubuntu.com/ubuntu jammy InRelease
Hit:5 http://in.archive.ubuntu.com/ubuntu jammy-updates InRelease
Hit:6 http://in.archive.ubuntu.com/ubuntu jammy-backports InRelease
Reading package lists... Done
W: GPG error: https://download.gocd.org  InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY D8843F288816C449
E: The repository 'https://download.gocd.org  InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

[chadlwilson]

It looks like you forgot the steps to download and import trust for the public key?

sudo install -m 0755 -d /etc/apt/keyrings
curl https://download.gocd.org/GOCD-GPG-KEY.asc | sudo gpg --dearmor -o /etc/apt/keyrings/gocd.gpg
sudo chmod a+r /etc/apt/keyrings/gocd.gpg