Restructure project layout

internal/api/middleware.go

@@ -0,0 +1,22 @@
+package api
+
+import (
+	"github.com/gin-gonic/gin"
+)
+
+type idInURI struct {
+	ID uint `uri:"id" binding:"required"`
+}
+
+// RequireIDInURI returns a Gin middleware which requires an ID to be supplied in the URI of the request.
+func RequireIDInURI() gin.HandlerFunc {
+	return func(ctx *gin.Context) {
+		var requestModel idInURI
+
+		if err := ctx.BindUri(&requestModel); err != nil {
+			return
+		}
+
+		ctx.Set("id", requestModel.ID)
+	}
+}