chore: fix setting user agent

internal/hooks/user_agent.go

@@ -0,0 +1,21 @@
+package hooks
+
+import (
+	"net/http"
+
+	"github.com/Kong/sdk-konnect-go/pkg/metadata"
+)
+
+type UserAgentPreRequestHook struct{}
+
+var _ beforeRequestHook = (*UserAgentPreRequestHook)(nil)
+
+func (i *UserAgentPreRequestHook) BeforeRequest(hookCtx BeforeRequestContext, req *http.Request) (*http.Request, error) {
+	ua := metadata.GetUserAgent()
+	if ua != "" {
+		req.Header.Set("User-Agent", ua)
+		return req, nil
+	}
+
+	return req, nil
+}

pkg/metadata/metadata.go

@@ -0,0 +1,24 @@
+package metadata
+
+import "sync"
+
+var (
+	l         sync.RWMutex
+	userAgent string
+)
+
+// SetUserAgent sets the user agent to be used by the SDK.
+// This is then used by UserAgentPreRequestHook in internal/hooks/user_agent.go
+func SetUserAgent(ua string) {
+	l.Lock()
+	defer l.Unlock()
+	userAgent = ua
+}
+
+// GetUserAgent returns the user agent to be used by the SDK.
+// This is then used by UserAgentPreRequestHook in internal/hooks/user_agent.go
+func GetUserAgent() string {
+	l.RLock()
+	defer l.RUnlock()
+	return userAgent
+}