slighty improvement of logging (#6)

app/context/context.go

@@ -12,10 +12,40 @@ import (
 type key uint32
 
 const (
-	converterKey key = iota
+	requestIDKey key = iota
+	converterKey
 	resultFilePathKey
 )
 
+// WithRequestID populates a request's context with the given request ID
+// and returns the updated request.
+func WithRequestID(r *http.Request, requestID string) *http.Request {
+	ctx := r.Context()
+	ctx = context.WithValue(ctx, requestIDKey, requestID)
+	r = r.WithContext(ctx)
+
+	return r
+}
+
+type requestIDNotFoundError struct{}
+
+const requestIDNotFoundErrorMessage = "the request ID was not found in request context"
+
+func (e *requestIDNotFoundError) Error() string {
+	return requestIDNotFoundErrorMessage
+}
+
+// GetRequestID returns the request ID if found in
+// the request's context. Otherwise throws an error.
+func GetRequestID(r *http.Request) (string, error) {
+	ID, ok := r.Context().Value(requestIDKey).(string)
+	if !ok {
+		return "", &requestIDNotFoundError{}
+	}
+
+	return ID, nil
+}
+
 // WithConverter populates a request's context with the given converter
 // and returns the updated request.
 func WithConverter(r *http.Request, converter *converter.Converter) *http.Request {