feat: transport inject request function

Signed-off-by: Eray Ates <[email protected]>

client.go

@@ -195,6 +195,7 @@ func New(opts ...OptionClientFn) (*Client, error) {
 		Base:    client.Transport,
 		Header:  o.Header,
 		BaseURL: baseURL,
+		Inject:  o.Inject,
 	}
 
 	if len(o.RoundTripperList) > 0 {

option.go

@@ -65,6 +65,9 @@ type optionClientValue struct {
 
 	// Proxy for http(s) requests.
 	Proxy string
+
+	// Inject extra content to request (e.g. tracing propagation).
+	Inject func(ctx context.Context, req *http.Request)
 }
 
 // OptionClientFn is a function that configures the client.
@@ -258,3 +261,14 @@ func WithProxy(proxy string) OptionClientFn {
 		options.Proxy = proxy
 	}
 }
+
+// WithInject configures the client to use the provided inject function.
+//
+//	func(ctx context.Context, req *http.Request) {
+//	  otel.GetTextMapPropagator().Inject(ctx, propagation.HeaderCarrier(req.Header))
+//	}
+func WithInject(inject func(ctx context.Context, req *http.Request)) OptionClientFn {
+	return func(options *optionClientValue) {
+		options.Inject = inject
+	}
+}

transport.go

@@ -1,6 +1,7 @@
 package klient
 
 import (
+	"context"
 	"net/http"
 	"net/url"
 )
@@ -15,6 +16,9 @@ type TransportKlient struct {
 	Header http.Header
 	// BaseURL is the base URL for relative requests.
 	BaseURL *url.URL
+
+	// Inject extra content to request (e.g. tracing propagation).
+	Inject func(ctx context.Context, req *http.Request)
 }
 
 var _ http.RoundTripper = (*TransportKlient)(nil)
@@ -51,6 +55,10 @@ func (t *TransportKlient) SetHeader(req *http.Request) {
 			req.Header[k] = v
 		}
 	}
+
+	if t.Inject != nil {
+		t.Inject(ctx, req)
+	}
 }
 
 // RoundTrip authorizes and authenticates the request with an