Emit a structured event with an allowlist

Useful logs have a stable schema and useful context. They should not become a dump of request bodies, tokens, headers or arbitrary internal objects.

The native task starts from a source Event that can contain a Sensitive map. Your job is to validate the approved fields and encode a smaller DTO. The negative fixture deliberately includes recognizable private markers so a leak cannot look like a passing test.

JSON encoding escapes representation; it does not decide whether a value should be logged. A blacklist of familiar secret names misses new fields and renamed data. An explicit small DTO makes omission the default.

The chosen event contains a server-owned ID, closed method/route labels, numeric status, optional duration and terminal outcome. Status zero means no final response was committed before a panic, not an invented HTTP 500.

package main
import ("fmt";"encoding/json")
func main(){
source:=map[string]string{"route":"/notes","body":"PRIVATE_FIXTURE"};selected:=map[string]string{"route":source["route"]};data,_:=json.Marshal(selected);fmt.Println(string(data))
}

Validate what remains. An arbitrary raw URL does not belong in the route field. An unknown outcome string could carry private error text and create unstable values. A negative duration is invalid, while nil and zero mean different things.

The download’s writer serializes one complete event line under a mutex. A sink error is reported through a separate trusted diagnostic callback; it does not turn an already valid API response into a different status. This synchronous small lab is not a full buffered logging pipeline.

Go’s slog offers richer logger/handler configuration. The optional primary talk and examples introduce that direction; Boot.dev continues into setup, storage, security and lifecycle. Keep the field-selection boundary when moving to a larger logger.

package main
import ("fmt";"bytes";"log/slog";"encoding/json")
func main(){
var buffer bytes.Buffer;logger:=slog.New(slog.NewJSONHandler(&buffer,nil));logger.Info("request","request_id","lab-1","route","/notes");var row map[string]any;_ =json.Unmarshal(buffer.Bytes(),&row);fmt.Println(row["request_id"],row["route"])
}

Complete the DTO serialization. Assert its exact field set, absence of private markers and the null/zero distinction. Do not treat a passing event test as proof about all framework or application logging outside this schema.

Next we count requests with a finite label space.