cluster: make unreachable panic explicit

making revive 1.3.4 happy

Signed-off-by: Alejandro Mery <amery@jpi.io>

pkg/cluster/cluster_file.go

@@ -33,7 +33,11 @@ func (m *Cluster) openWriter(name string, flags int, args ...any) (io.WriteClose
 		return nil, err
 	}
 
-	return f.(io.WriteCloser), nil
+	if f, ok := f.(io.WriteCloser); ok {
+		return f, nil
+	}
+
+	panic("unreachable")
 }
 
 // ReadFile reads a file from the cluster's config directory

pkg/cluster/machine_file.go

@@ -34,7 +34,11 @@ func (m *Machine) openWriter(name string, flags int, args ...any) (io.WriteClose
 		return nil, err
 	}
 
-	return f.(io.WriteCloser), nil
+	if f, ok := f.(io.WriteCloser); ok {
+		return f, nil
+	}
+
+	panic("unreachable")
 }
 
 // RemoveFile deletes a file from the machine's config directory