Create viewer package.

The "viewer" is the user/authenticated session browsing the site.

pkg/viewer/viewr.go

@@ -0,0 +1,27 @@
+// Package viewer provides utility functions for passing the current user to a context.
+package viewer
+
+import "context"
+
+type key int
+
+const viewerKey key = 0
+
+// Viewer represents a user performing an action on the server.
+type Viewer struct {
+	UserID    string
+	Username  string
+	FullName  string
+	SessionID string
+}
+
+// FromContext returns the current user information if present.
+func FromContext(ctx context.Context) (Viewer, bool) {
+	v, ok := ctx.Value(viewerKey).(Viewer)
+	return v, ok
+}
+
+// NewContext updates the parent context with viewer information.
+func NewContext(ctx context.Context, v Viewer) context.Context {
+	return context.WithValue(ctx, viewerKey, v)
+}