feat(go): add exception group changes (#15139)

Author: giortzisg

platform-includes/capture-error/go.mdx

@@ -1,4 +1,12 @@
-To capture an event in Go, you can pass any struct implementing an `error` interface to `CaptureException()`. If you use a 3rd party library instead of the native `errors` package and it implements the `Unwrap() error` or `Cause() error` method, we'll follow the chain of errors and extract the stack trace from the root cause.
+To capture an event in Go, you can pass any struct implementing an `error` interface to `CaptureException()`. The SDK automatically unwraps and captures all errors in the error chain, providing comprehensive error context to Sentry. The SDK also supports third-party libraries and extracts all stack traces in the chain.
+
+## Error Unwrapping
+
+The SDK supports multiple error wrapping patterns:
+
+- **Standard library**: `fmt.Errorf` with `%w` and `errors.Join` (Go 1.20+)
+- **Single error chains**: Errors implementing `Unwrap() error`
+- **Third-party libraries**: Errors implementing `Cause() error`
 
 The SDK is fully compatible with (but not limited to):
 
@@ -9,6 +17,23 @@ The SDK is fully compatible with (but not limited to):
 
 If there is an errors package that's not working out of the box, let us know!
 
+## Exception Groups
+
+When you use `errors.Join` to combine multiple errors, the SDK captures them as an **exception group**. This allows you to see all related errors together in Sentry, properly structured with their relationships preserved.
+
+```go
+err1 := errors.New("first error")
+err2 := errors.New("second error")
+joinedErr := errors.Join(err1, err2)
+
+// This will be captured as an exception group in Sentry
+sentry.CaptureException(joinedErr)
+```
+
+For errors wrapped with `fmt.Errorf` or single-error chains, the SDK captures each error in the chain individually, maintaining the causal relationship.
+
+## Basic Example
+
 ```go
 f, err := os.Open("filename.ext")
 if err != nil {