update readme

README.md

@@ -77,6 +77,7 @@ console.log(farewell); // => 👈 goodbye
 
 - [Validation](/recipes/validation.md)
 - [Authorization](/recipes/authorization.md)
+- [Error Handling](/recipes/error-handling.md)
 
 Learn more about tRPC.io [here](https://trpc.io/docs).
 

recipes/error-handling.md

@@ -0,0 +1,15 @@
+## Handling errors
+
+All errors that occur in a procedure go through the `onError` method before being sent to the client. Here you can handle or change errors.
+
+```ts
+// ~/server/trpc/index.ts
+import * as trpc from '@trpc/server'
+
+export function onError({ error, type, path, input, ctx, req }) {
+  console.error('Error:', error)
+  if (error.code === 'INTERNAL_SERVER_ERROR') {
+    // send to bug reporting
+  }
+}
+```