typecast safety example

Author: giortzisg

docs/platforms/go/common/tracing/instrumentation/custom-instrumentation/index.mdx

@@ -71,12 +71,16 @@ http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
 Or you can update existing transaction and span data by:
 
 ```go
-if d := transaction.Data["dataAttr1"]; d != nil {
-  transaction.SetData("dataAttr1", d.(int)+42)
+if d, found := transaction.Data["dataAttr1"]; found {
+  if dataAttr1, ok := d.(int); ok {
+    transaction.SetData("dataAttr1", dataAttr1.(int)+42)
+  }
 }
 
-if d := span.Data["dataAttr1"]; d != nil {
-  span.SetData("dataAttr1", d.(int)+42)
+if d, found := span.Data["dataAttr1"]; found {
+  if dataAttr1, ok := d.(int); ok {
+    span.SetData("dataAttr1", dataAttr1.(int)+42)
+  }
 }
 })
 ```