add riscv64 support

flake.nix

@@ -16,9 +16,15 @@
       };
       defaultTemplate = self.templates.app;
 
-    } //
-    (flake-utils.lib.eachDefaultSystem
-      (system:
+    }
+    // (flake-utils.lib.eachSystem
+      [
+        "x86_64-linux"
+        "aarch64-linux"
+        "riscv64-linux"
+      ]
+      (
+        system:
         let
           pkgs = nixpkgs.legacyPackages.${system};
 
@@ -44,6 +50,7 @@
           devShells.default = callPackage ./shell.nix {
             inherit mkGoEnv gomod2nix;
           };
-        })
+        }
+      )
     );
 }