ci: force GO_VERSION (#1204)

(cherry picked from commit a7c48ef)

Author: v1v

.ci/Jenkinsfile

@@ -61,6 +61,8 @@ pipeline {
           setEnvVar('K8S_CHANGES', isGitRegionMatch(patterns: [ '(^deploy/kubernetes/.*|^version/docs/version.asciidoc|.ci/Jenkinsfile)' ], shouldMatchAll: false).toString())
           setEnvVar('EXT_WINDOWS_CHANGES', isGitRegionMatch(patterns: [ '.ci/Jenkinsfile' ], shouldMatchAll: false).toString())
           setEnvVar('EXT_M1_CHANGES', isGitRegionMatch(patterns: [ '.ci/Jenkinsfile' ], shouldMatchAll: false).toString())
+          // set the GO_VERSION env variable with the go version to be used in withMageEnv
+          setEnvVar('GO_VERSION', readFile(file: '.go-version')?.trim())
         }
       }
     }