raphael · Nov 9, 2026 · Nov 9, 2026
diff --git a/upload_download/cmd/upload_download/main.go b/upload_download/cmd/upload_download/main.go
@@ -13,7 +13,7 @@ import (
 	"syscall"
 
 	uploaddownload "goa.design/examples/upload_download"
-	"goa.design/examples/upload_download/gen/updown"
+	genupdown "goa.design/examples/upload_download/gen/updown"
 )
 
 func main() {
@@ -36,19 +36,27 @@ func main() {
 		logger = log.New(os.Stderr, "[upload-download] ", log.Ltime)
 	}
 
-	// Initialize the services.
-	updownSvc, err := uploaddownload.NewUpdown(*dirF, logger)
+	// Open the root directory used to confine uploaded and downloaded files.
+	root, err := os.OpenRoot(*dirF)
 	if err != nil {
 		logger.Fatal(err.Error())
 	}
+	defer func() {
+		if closeErr := root.Close(); closeErr != nil {
+			logger.Printf("failed to close root directory: %v", closeErr)
+		}
+	}()
+
+	// Initialize the services.
+	updownSvc := uploaddownload.NewUpdown(root, logger)
 
 	// Wrap the services in endpoints that can be invoked from other services
 	// potentially running in different processes.
 	var (
-		updownEndpoints *updown.Endpoints
+		updownEndpoints *genupdown.Endpoints
 	)
 	{
-		updownEndpoints = updown.NewEndpoints(updownSvc)
+		updownEndpoints = genupdown.NewEndpoints(updownSvc)
 	}
 
 	// Create channel used by both the signal handler and server goroutines

diff --git a/upload_download/design/design.go b/upload_download/design/design.go
@@ -39,6 +39,7 @@ incompatible with gRPC.`)
 
 		Error("invalid_media_type", ErrorResult, "Error returned when the Content-Type header does not define a multipart request.")
 		Error("invalid_multipart_request", ErrorResult, "Error returned when the request body is not a valid multipart content.")
+		Error("invalid_file_path", ErrorResult, "Error returned when the upload directory path is invalid.")
 		Error("internal_error", ErrorResult, "Fault while processing upload.")
 
 		HTTP(func() {
@@ -53,6 +54,7 @@ incompatible with gRPC.`)
 			// Define error HTTP statuses.
 			Response("invalid_media_type", StatusBadRequest)
 			Response("invalid_multipart_request", StatusBadRequest)
+			Response("invalid_file_path", StatusBadRequest)
 			Response("internal_error", StatusInternalServerError)
 		})
 	})

diff --git a/upload_download/gen/http/openapi.json b/upload_download/gen/http/openapi.json
diff --git a/upload_download/gen/http/openapi.yaml b/upload_download/gen/http/openapi.yaml
@@ -83,15 +83,15 @@ paths:
                 "204":
                     description: No Content response.
                 "400":
-                    description: 'invalid_multipart_request: Error returned when the request body is not a valid multipart content.'
+                    description: 'invalid_file_path: Error returned when the upload directory path is invalid.'
                     schema:
-                        $ref: '#/definitions/UpdownUploadInvalidMultipartRequestResponseBody'
+                        $ref: '#/definitions/UpdownUploadInvalidFilePathResponseBody'
                     examples:
                         application/vnd.goa.error:
                             fault: false
                             id: 123abc
                             message: parameter 'p' must be an integer
-                            name: invalid_multipart_request
+                            name: invalid_file_path
                             temporary: false
                             timeout: false
                 "500":
@@ -238,6 +238,49 @@ definitions:
             - temporary
             - timeout
             - fault
+    UpdownUploadInvalidFilePathResponseBody:
+        title: 'Mediatype identifier: application/vnd.goa.error; view=default'
+        type: object
+        properties:
+            fault:
+                type: boolean
+                description: Is the error a server-side fault?
+                example: false
+            id:
+                type: string
+                description: ID is a unique identifier for this particular occurrence of the problem.
+                example: 123abc
+            message:
+                type: string
+                description: Message is a human-readable explanation specific to this occurrence of the problem.
+                example: parameter 'p' must be an integer
+            name:
+                type: string
+                description: Name is the name of this class of errors.
+                example: bad_request
+            temporary:
+                type: boolean
+                description: Is the error temporary?
+                example: false
+            timeout:
+                type: boolean
+                description: Is the error a timeout?
+                example: true
+        description: Error response result type (default view)
+        example:
+            fault: false
+            id: 123abc
+            message: parameter 'p' must be an integer
+            name: bad_request
+            temporary: false
+            timeout: true
+        required:
+            - name
+            - id
+            - message
+            - temporary
+            - timeout
+            - fault
     UpdownUploadInvalidMediaTypeResponseBody:
         title: 'Mediatype identifier: application/vnd.goa.error; view=default'
         type: object

diff --git a/upload_download/gen/http/openapi3.2.json b/upload_download/gen/http/openapi3.2.json
@@ -1 +1 @@
-{"openapi":"3.2.0","info":{"title":"Goa API","description":"Simple file upload and download example.","version":"0.0.1"},"servers":[{"url":"http://localhost:80","name":"upload_download","description":"Default server for upload_download"}],"paths":{"/download/{filename}":{"get":{"tags":["updown"],"summary":"download updown","operationId":"updown#download","parameters":[{"name":"filename","in":"path","description":"Path to downloaded file.","required":true,"schema":{"type":"string","description":"Path to downloaded file.","example":"Ut rerum est minus natus voluptas ex."},"example":"Ut rerum est minus natus voluptas ex."}],"responses":{"200":{"description":"OK response.","headers":{"Content-Length":{"description":"Length is the downloaded content length in bytes.","schema":{"type":"integer","description":"Length is the downloaded content length in bytes.","example":4194304,"format":"int64"},"example":4194304}},"content":{"application/json":{"schema":{"type":"string","format":"binary"}}}},"404":{"description":"invalid_file_path: Could not locate file for download","content":{"application/vnd.goa.error":{"schema":{"$ref":"#/components/schemas/Error"},"example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"invalid_file_path","temporary":false,"timeout":false}}}},"500":{"description":"internal_error: Fault while processing download.","content":{"application/vnd.goa.error":{"schema":{"$ref":"#/components/schemas/Error"},"example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"internal_error","temporary":false,"timeout":false}}}}}}},"/upload/{dir}":{"post":{"tags":["updown"],"summary":"upload updown","operationId":"updown#upload","parameters":[{"name":"dir","in":"path","description":"Dir is the relative path to the file directory where the uploaded content is saved.","required":true,"schema":{"type":"string","description":"Dir is the relative path to the file directory where the uploaded content is saved.","default":"upload","example":"upload"},"example":"upload"},{"name":"Content-Type","in":"header","description":"Content-Type header, must define value for multipart boundary.","schema":{"type":"string","description":"Content-Type header, must define value for multipart boundary.","default":"multipart/form-data; boundary=goa","example":"multipart/form-data; boundary=goa","pattern":"multipart/[^;]+; boundary=.+"},"example":"multipart/form-data; boundary=goa"}],"responses":{"204":{"description":"No Content response."},"400":{"description":"invalid_multipart_request: Error returned when the request body is not a valid multipart content.","content":{"application/vnd.goa.error":{"schema":{"$ref":"#/components/schemas/Error"},"example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"invalid_multipart_request","temporary":false,"timeout":false}}}},"500":{"description":"internal_error: Fault while processing upload.","content":{"application/vnd.goa.error":{"schema":{"$ref":"#/components/schemas/Error"},"example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"internal_error","temporary":false,"timeout":false}}}}}}}},"components":{"schemas":{"Error":{"type":"object","properties":{"fault":{"type":"boolean","description":"Is the error a server-side fault?","example":false},"id":{"type":"string","description":"ID is a unique identifier for this particular occurrence of the problem.","example":"123abc"},"message":{"type":"string","description":"Message is a human-readable explanation specific to this occurrence of the problem.","example":"parameter 'p' must be an integer"},"name":{"type":"string","description":"Name is the name of this class of errors.","example":"bad_request"},"temporary":{"type":"boolean","description":"Is the error temporary?","example":false},"timeout":{"type":"boolean","description":"Is the error a timeout?","example":false}},"description":"Error response result type","example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"bad_request","temporary":false,"timeout":false},"required":["name","id","message","temporary","timeout","fault"]}}},"tags":[{"name":"updown","description":"Service updown demonstrates how to implement upload and download of files in\nGoa without having to load the entire content in memory first.\nThe upload method uses SkipRequestBodyEncodeDecode to delegate reading the HTTP\nrequest body to the service logic. This alleviates the need for loading the\nfull body content in memory first to decode it into a data structure. Note that\nusing SkipRequestBodyDecode is incompatible with gRPC and can only be used on\nmethods that only define a HTTP transport mapping. This example implementation\nleverages package \"mime/multipart\" to read the request body.\nSimilarly the download method uses SkipResponseBodyEncodeDecode to stream the \nfile to the client without requiring to load the complete content in memory\nfirst. As with SkipRequestBodyDecode using SkipResponseBodyEncodeDecode is\nincompatible with gRPC."}]}
+{"openapi":"3.2.0","info":{"title":"Goa API","description":"Simple file upload and download example.","version":"0.0.1"},"servers":[{"url":"http://localhost:80","name":"upload_download","description":"Default server for upload_download"}],"paths":{"/download/{filename}":{"get":{"tags":["updown"],"summary":"download updown","operationId":"updown#download","parameters":[{"name":"filename","in":"path","description":"Path to downloaded file.","required":true,"schema":{"type":"string","description":"Path to downloaded file.","example":"Ut rerum est minus natus voluptas ex."},"example":"Ut rerum est minus natus voluptas ex."}],"responses":{"200":{"description":"OK response.","headers":{"Content-Length":{"description":"Length is the downloaded content length in bytes.","schema":{"type":"integer","description":"Length is the downloaded content length in bytes.","example":4194304,"format":"int64"},"example":4194304}},"content":{"application/json":{"schema":{"type":"string","format":"binary"}}}},"404":{"description":"invalid_file_path: Could not locate file for download","content":{"application/vnd.goa.error":{"schema":{"$ref":"#/components/schemas/Error"},"example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"invalid_file_path","temporary":false,"timeout":false}}}},"500":{"description":"internal_error: Fault while processing download.","content":{"application/vnd.goa.error":{"schema":{"$ref":"#/components/schemas/Error"},"example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"internal_error","temporary":false,"timeout":false}}}}}}},"/upload/{dir}":{"post":{"tags":["updown"],"summary":"upload updown","operationId":"updown#upload","parameters":[{"name":"dir","in":"path","description":"Dir is the relative path to the file directory where the uploaded content is saved.","required":true,"schema":{"type":"string","description":"Dir is the relative path to the file directory where the uploaded content is saved.","default":"upload","example":"upload"},"example":"upload"},{"name":"Content-Type","in":"header","description":"Content-Type header, must define value for multipart boundary.","schema":{"type":"string","description":"Content-Type header, must define value for multipart boundary.","default":"multipart/form-data; boundary=goa","example":"multipart/form-data; boundary=goa","pattern":"multipart/[^;]+; boundary=.+"},"example":"multipart/form-data; boundary=goa"}],"responses":{"204":{"description":"No Content response."},"400":{"description":"invalid_file_path: Error returned when the upload directory path is invalid.","content":{"application/vnd.goa.error":{"schema":{"$ref":"#/components/schemas/Error"},"example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"invalid_file_path","temporary":false,"timeout":false}}}},"500":{"description":"internal_error: Fault while processing upload.","content":{"application/vnd.goa.error":{"schema":{"$ref":"#/components/schemas/Error"},"example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"internal_error","temporary":false,"timeout":false}}}}}}}},"components":{"schemas":{"Error":{"type":"object","properties":{"fault":{"type":"boolean","description":"Is the error a server-side fault?","example":false},"id":{"type":"string","description":"ID is a unique identifier for this particular occurrence of the problem.","example":"123abc"},"message":{"type":"string","description":"Message is a human-readable explanation specific to this occurrence of the problem.","example":"parameter 'p' must be an integer"},"name":{"type":"string","description":"Name is the name of this class of errors.","example":"bad_request"},"temporary":{"type":"boolean","description":"Is the error temporary?","example":false},"timeout":{"type":"boolean","description":"Is the error a timeout?","example":false}},"description":"Error response result type","example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"bad_request","temporary":false,"timeout":false},"required":["name","id","message","temporary","timeout","fault"]}}},"tags":[{"name":"updown","description":"Service updown demonstrates how to implement upload and download of files in\nGoa without having to load the entire content in memory first.\nThe upload method uses SkipRequestBodyEncodeDecode to delegate reading the HTTP\nrequest body to the service logic. This alleviates the need for loading the\nfull body content in memory first to decode it into a data structure. Note that\nusing SkipRequestBodyDecode is incompatible with gRPC and can only be used on\nmethods that only define a HTTP transport mapping. This example implementation\nleverages package \"mime/multipart\" to read the request body.\nSimilarly the download method uses SkipResponseBodyEncodeDecode to stream the \nfile to the client without requiring to load the complete content in memory\nfirst. As with SkipRequestBodyDecode using SkipResponseBodyEncodeDecode is\nincompatible with gRPC."}]}
diff --git a/upload_download/gen/http/openapi3.2.yaml b/upload_download/gen/http/openapi3.2.yaml
@@ -98,7 +98,7 @@ paths:
                 "204":
                     description: No Content response.
                 "400":
-                    description: 'invalid_multipart_request: Error returned when the request body is not a valid multipart content.'
+                    description: 'invalid_file_path: Error returned when the upload directory path is invalid.'
                     content:
                         application/vnd.goa.error:
                             schema:
@@ -107,7 +107,7 @@ paths:
                                 fault: false
                                 id: 123abc
                                 message: parameter 'p' must be an integer
-                                name: invalid_multipart_request
+                                name: invalid_file_path
                                 temporary: false
                                 timeout: false
                 "500":
Original file line number	Diff line number	Diff line change
		@@ -1 +1 @@
		{"openapi":"3.2.0","info":{"title":"Goa API","description":"Simple file upload and download example.","version":"0.0.1"},"servers":[{"url":"http://localhost:80","name":"upload_download","description":"Default server for upload_download"}],"paths":{"/download/{filename}":{"get":{"tags":["updown"],"summary":"download updown","operationId":"updown#download","parameters":[{"name":"filename","in":"path","description":"Path to downloaded file.","required":true,"schema":{"type":"string","description":"Path to downloaded file.","example":"Ut rerum est minus natus voluptas ex."},"example":"Ut rerum est minus natus voluptas ex."}],"responses":{"200":{"description":"OK response.","headers":{"Content-Length":{"description":"Length is the downloaded content length in bytes.","schema":{"type":"integer","description":"Length is the downloaded content length in bytes.","example":4194304,"format":"int64"},"example":4194304}},"content":{"application/json":{"schema":{"type":"string","format":"binary"}}}},"404":{"description":"invalid_file_path: Could not locate file for download","content":{"application/vnd.goa.error":{"schema":{"$ref":"#/components/schemas/Error"},"example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"invalid_file_path","temporary":false,"timeout":false}}}},"500":{"description":"internal_error: Fault while processing download.","content":{"application/vnd.goa.error":{"schema":{"$ref":"#/components/schemas/Error"},"example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"internal_error","temporary":false,"timeout":false}}}}}}},"/upload/{dir}":{"post":{"tags":["updown"],"summary":"upload updown","operationId":"updown#upload","parameters":[{"name":"dir","in":"path","description":"Dir is the relative path to the file directory where the uploaded content is saved.","required":true,"schema":{"type":"string","description":"Dir is the relative path to the file directory where the uploaded content is saved.","default":"upload","example":"upload"},"example":"upload"},{"name":"Content-Type","in":"header","description":"Content-Type header, must define value for multipart boundary.","schema":{"type":"string","description":"Content-Type header, must define value for multipart boundary.","default":"multipart/form-data; boundary=goa","example":"multipart/form-data; boundary=goa","pattern":"multipart/[^;]+; boundary=.+"},"example":"multipart/form-data; boundary=goa"}],"responses":{"204":{"description":"No Content response."},"400":{"description":"invalid_multipart_request: Error returned when the request body is not a valid multipart content.","content":{"application/vnd.goa.error":{"schema":{"$ref":"#/components/schemas/Error"},"example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"invalid_multipart_request","temporary":false,"timeout":false}}}},"500":{"description":"internal_error: Fault while processing upload.","content":{"application/vnd.goa.error":{"schema":{"$ref":"#/components/schemas/Error"},"example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"internal_error","temporary":false,"timeout":false}}}}}}}},"components":{"schemas":{"Error":{"type":"object","properties":{"fault":{"type":"boolean","description":"Is the error a server-side fault?","example":false},"id":{"type":"string","description":"ID is a unique identifier for this particular occurrence of the problem.","example":"123abc"},"message":{"type":"string","description":"Message is a human-readable explanation specific to this occurrence of the problem.","example":"parameter 'p' must be an integer"},"name":{"type":"string","description":"Name is the name of this class of errors.","example":"bad_request"},"temporary":{"type":"boolean","description":"Is the error temporary?","example":false},"timeout":{"type":"boolean","description":"Is the error a timeout?","example":false}},"description":"Error response result type","example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"bad_request","temporary":false,"timeout":false},"required":["name","id","message","temporary","timeout","fault"]}}},"tags":[{"name":"updown","description":"Service updown demonstrates how to implement upload and download of files in\nGoa without having to load the entire content in memory first.\nThe upload method uses SkipRequestBodyEncodeDecode to delegate reading the HTTP\nrequest body to the service logic. This alleviates the need for loading the\nfull body content in memory first to decode it into a data structure. Note that\nusing SkipRequestBodyDecode is incompatible with gRPC and can only be used on\nmethods that only define a HTTP transport mapping. This example implementation\nleverages package \"mime/multipart\" to read the request body.\nSimilarly the download method uses SkipResponseBodyEncodeDecode to stream the \nfile to the client without requiring to load the complete content in memory\nfirst. As with SkipRequestBodyDecode using SkipResponseBodyEncodeDecode is\nincompatible with gRPC."}]}
		{"openapi":"3.2.0","info":{"title":"Goa API","description":"Simple file upload and download example.","version":"0.0.1"},"servers":[{"url":"http://localhost:80","name":"upload_download","description":"Default server for upload_download"}],"paths":{"/download/{filename}":{"get":{"tags":["updown"],"summary":"download updown","operationId":"updown#download","parameters":[{"name":"filename","in":"path","description":"Path to downloaded file.","required":true,"schema":{"type":"string","description":"Path to downloaded file.","example":"Ut rerum est minus natus voluptas ex."},"example":"Ut rerum est minus natus voluptas ex."}],"responses":{"200":{"description":"OK response.","headers":{"Content-Length":{"description":"Length is the downloaded content length in bytes.","schema":{"type":"integer","description":"Length is the downloaded content length in bytes.","example":4194304,"format":"int64"},"example":4194304}},"content":{"application/json":{"schema":{"type":"string","format":"binary"}}}},"404":{"description":"invalid_file_path: Could not locate file for download","content":{"application/vnd.goa.error":{"schema":{"$ref":"#/components/schemas/Error"},"example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"invalid_file_path","temporary":false,"timeout":false}}}},"500":{"description":"internal_error: Fault while processing download.","content":{"application/vnd.goa.error":{"schema":{"$ref":"#/components/schemas/Error"},"example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"internal_error","temporary":false,"timeout":false}}}}}}},"/upload/{dir}":{"post":{"tags":["updown"],"summary":"upload updown","operationId":"updown#upload","parameters":[{"name":"dir","in":"path","description":"Dir is the relative path to the file directory where the uploaded content is saved.","required":true,"schema":{"type":"string","description":"Dir is the relative path to the file directory where the uploaded content is saved.","default":"upload","example":"upload"},"example":"upload"},{"name":"Content-Type","in":"header","description":"Content-Type header, must define value for multipart boundary.","schema":{"type":"string","description":"Content-Type header, must define value for multipart boundary.","default":"multipart/form-data; boundary=goa","example":"multipart/form-data; boundary=goa","pattern":"multipart/[^;]+; boundary=.+"},"example":"multipart/form-data; boundary=goa"}],"responses":{"204":{"description":"No Content response."},"400":{"description":"invalid_file_path: Error returned when the upload directory path is invalid.","content":{"application/vnd.goa.error":{"schema":{"$ref":"#/components/schemas/Error"},"example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"invalid_file_path","temporary":false,"timeout":false}}}},"500":{"description":"internal_error: Fault while processing upload.","content":{"application/vnd.goa.error":{"schema":{"$ref":"#/components/schemas/Error"},"example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"internal_error","temporary":false,"timeout":false}}}}}}}},"components":{"schemas":{"Error":{"type":"object","properties":{"fault":{"type":"boolean","description":"Is the error a server-side fault?","example":false},"id":{"type":"string","description":"ID is a unique identifier for this particular occurrence of the problem.","example":"123abc"},"message":{"type":"string","description":"Message is a human-readable explanation specific to this occurrence of the problem.","example":"parameter 'p' must be an integer"},"name":{"type":"string","description":"Name is the name of this class of errors.","example":"bad_request"},"temporary":{"type":"boolean","description":"Is the error temporary?","example":false},"timeout":{"type":"boolean","description":"Is the error a timeout?","example":false}},"description":"Error response result type","example":{"fault":false,"id":"123abc","message":"parameter 'p' must be an integer","name":"bad_request","temporary":false,"timeout":false},"required":["name","id","message","temporary","timeout","fault"]}}},"tags":[{"name":"updown","description":"Service updown demonstrates how to implement upload and download of files in\nGoa without having to load the entire content in memory first.\nThe upload method uses SkipRequestBodyEncodeDecode to delegate reading the HTTP\nrequest body to the service logic. This alleviates the need for loading the\nfull body content in memory first to decode it into a data structure. Note that\nusing SkipRequestBodyDecode is incompatible with gRPC and can only be used on\nmethods that only define a HTTP transport mapping. This example implementation\nleverages package \"mime/multipart\" to read the request body.\nSimilarly the download method uses SkipResponseBodyEncodeDecode to stream the \nfile to the client without requiring to load the complete content in memory\nfirst. As with SkipRequestBodyDecode using SkipResponseBodyEncodeDecode is\nincompatible with gRPC."}]}