use the stacktrace of cause, if that doesn't have one, use the one fr…

…om err

client.go

@@ -709,7 +709,7 @@ func (client *Client) CaptureError(err error, tags map[string]string, interfaces
 	extra := extractExtra(err)
 	cause := pkgErrors.Cause(err)
 
-	packet := NewPacketWithExtra(err.Error(), extra, append(append(interfaces, client.context.interfaces()...), NewException(cause, GetOrNewStacktrace(cause, 1, 3, client.includePaths)))...)
+	packet := NewPacketWithExtra(err.Error(), extra, append(append(interfaces, client.context.interfaces()...), NewException(cause, GetOrNewStacktrace(err, cause, 1, 3, client.includePaths)))...)
 	eventID, _ := client.Capture(packet, tags)
 
 	return eventID
@@ -734,7 +734,7 @@ func (client *Client) CaptureErrorAndWait(err error, tags map[string]string, int
 	extra := extractExtra(err)
 	cause := pkgErrors.Cause(err)
 
-	packet := NewPacketWithExtra(err.Error(), extra, append(append(interfaces, client.context.interfaces()...), NewException(cause, GetOrNewStacktrace(cause, 1, 3, client.includePaths)))...)
+	packet := NewPacketWithExtra(err.Error(), extra, append(append(interfaces, client.context.interfaces()...), NewException(cause, GetOrNewStacktrace(err, cause, 1, 3, client.includePaths)))...)
 	eventID, ch := client.Capture(packet, tags)
 	if eventID != "" {
 		<-ch

stacktrace.go

@@ -52,12 +52,24 @@ type StacktraceFrame struct {
 	InApp        bool     `json:"in_app"`
 }
 
+type StackTracer interface {
+	StackTrace() errors.StackTrace
+}
+
 // Try to get stacktrace from err as an interface of github.com/pkg/errors, or else NewStacktrace()
-func GetOrNewStacktrace(err error, skip int, context int, appPackagePrefixes []string) *Stacktrace {
-	stacktracer, errHasStacktrace := err.(interface {
-		StackTrace() errors.StackTrace
-	})
-	if errHasStacktrace {
+func GetOrNewStacktrace(err, cause error, skip int, context int, appPackagePrefixes []string) *Stacktrace {
+	// use the stacktrace of cause
+	var stacktracer StackTracer
+	var causeHasStacktrace, errHasStacktrace bool
+	stacktracer, causeHasStacktrace = cause.(StackTracer)
+
+	// if cause doesn't have a stacktrace, use the one of err
+	if !causeHasStacktrace {
+		stacktracer, errHasStacktrace = err.(StackTracer)
+	}
+
+	// if either has a trace, we can generate from it
+	if causeHasStacktrace || errHasStacktrace {
 		var frames []*StacktraceFrame
 		for _, f := range stacktracer.StackTrace() {
 			pc := uintptr(f) - 1