use async, respecting the function decl itself

src/cli.ts

@@ -243,7 +243,7 @@ function cli(args: string[]) {
     .addCommand(verify)
     .addCommand(calldata)
     // teardown to terminate SnarkJS, otherwise hangs the program
-    .hook('postAction', () => teardown())
+    .hook('postAction', async () => await teardown())
     .parse(args);
 
   // TODO: test graceful exits

src/utils/teardown.ts

@@ -1,8 +1,15 @@
 declare global {
   // eslint-disable-next-line no-var
-  var curve_bn128: {terminate: () => void} | undefined;
+  var curve_bn128: {terminate: () => Promise<void>} | undefined;
 }
 
-export function teardown() {
-  if (globalThis.curve_bn128) globalThis.curve_bn128.terminate();
+/**
+ * Teardown function to be run for graceful exits.
+ *
+ * SnarkJS may attach curve_bn128 to global, but does not terminate it.
+ * We have to do it manually (see https://github.com/iden3/snarkjs/issues/152)
+ * For this, we use the [`terminate`](https://github.com/iden3/ffjavascript/blob/master/src/bn128.js#L48) function.
+ */
+export async function teardown() {
+  if (globalThis.curve_bn128) await globalThis.curve_bn128.terminate();
 }