rules:
  - id: return-nil
    patterns:
        - pattern-either:
              - pattern: |
                      if $X == nil {
                              return $X
                      }
              - pattern: |
                      if $X != nil {
                              return ...
                      }
                      return $X
    message: "return nil instead of nil value"
    languages: [go]
    severity: ERROR