Update .github/workflows/build.yml

Co-authored-by: per1234 <[email protected]>

Author: kittaakos

Diff for: .github/workflows/build.yml

@@ -43,7 +43,7 @@ jobs:
             certificate-secret: WINDOWS_SIGNING_CERTIFICATE_PFX # Name of the secret that contains the certificate.
             certificate-password-secret: WINDOWS_SIGNING_CERTIFICATE_PASSWORD # Name of the secret that contains the certificate password.
             certificate-extension: pfx  # File extension for the certificate.
-          - os: ubuntu-latest
+          - os: ubuntu-20.04
           - os: macos-latest
             # APPLE_SIGNING_CERTIFICATE_P12 secret was produced by following the procedure from:
             # https://www.kencochrane.com/2020/08/01/build-and-sign-golang-binaries-for-macos-with-github-actions/#exporting-the-developer-certificate