File 'repomd.xml' from repository 'Google-Chrome' is signed with an unknown key '1397BC53640DB551'

I want to install Google Chrome on my OpenSuSE V42,3 Linux desktop computer. So, after adding the repository from google, my /etc/zypp/repos.d/Google-Chrome.repo is as shown as follow:

[Google-Chrome]
name=Google-Chrome
enabled=1
autorefresh=1
baseurl=http://dl.google.com/linux/chrome/rpm/stable/x86_64
type=rpm-md
keeppackages=0
Google-Chrome.repo

Now, every time when I try to perform an update using zypper up, I get a warning message as shown below. What should I do?

[root@linux:/etc/zypp/repos.d 15%] # zypper up
Retrieving repository 'Google-Chrome' metadata ----------------------------------------------------------------------------------\]
Warning: File 'repomd.xml' from repository 'Google-Chrome' is signed with an unknown key '1397BC53640DB551'.

    Note: Signing data enables the recipient to verify that no modifications occurred after the data
    were signed. Accepting data with no, wrong or unknown signature can lead to a corrupted system
    and in extreme cases even to a system compromise.

    Note: File 'repomd.xml' is the repositories master index file. It ensures the integrity of the
    whole repo.

    Warning: We can't verify that no one meddled with this file, so it might not be trustworthy
    anymore! You should not continue unless you know it's safe.

**File 'repomd.xml' from repository 'Google-Chrome' is signed with an unknown key '1397BC53640DB551'. Continue? [yes/no] (no):**

did you import google’s pgp key?

sudo rpm --import https://dl.google.com/linux/linux_signing_key.pub