Object Storage Service:Download an object using a presigned URL (Go SDK V2)

To download a versioned object, include the VersionId field in GetObjectRequest.

result, err := client.Presign(context.TODO(), &oss.GetObjectRequest{
    Bucket:    oss.Ptr(bucketName),
    Key:       oss.Ptr(objectName),
    VersionId: oss.Ptr("yourVersionId"), // Specify the version ID.
},
    oss.PresignExpires(10*time.Minute),
)
if err != nil {
    log.Fatalf("failed to presign GetObject request: %v", err)
}
log.Printf("Presign result: %#v\n", result)
log.Printf("URL: %#v\n", result.URL)

By default, browsers may render objects such as images or HTML files inline. To force a download prompt, set the response-content-disposition parameter when generating the URL.

Step 1: Generate the URL with `ResponseContentDisposition`.

result, err := client.Presign(context.TODO(), &oss.GetObjectRequest{
    Bucket:                     oss.Ptr(bucketName),
    Key:                        oss.Ptr(objectName),
    ResponseContentDisposition: oss.Ptr("attachment;filename=test.txt"),
},
)
if err != nil {
    log.Fatalf("failed to presign GetObject request: %v", err)
}
log.Printf("Method: %v\n", result.Method)
log.Printf("Expiration: %v\n", result.Expiration)
log.Printf("URL: %v\n", result.URL)

Step 2: Download using the URL — no additional headers required.

curl:

curl -X GET "https://examplebucket.oss-cn-hangzhou.aliyuncs.com/exampleobject.txt?response-content-disposition=attachment%3B%20filename%3Dtest.txt&x-oss-date=20241113T093321Z&x-oss-expires=3599&x-oss-signature-version=OSS4-HMAC-SHA256&x-oss-credential=LTAI****************&x-oss-signature=ed5a******************************************************" \
-o "myfile.txt"

Go:

package main

import (
	"io"
	"log"
	"net/http"
	"os"
)

func main() {
	url := "https://examplebucket.oss-cn-hangzhou.aliyuncs.com/exampleobject.txt?response-content-disposition=attachment%3B%20filename%3Dtest.txt&x-oss-date=20241112T092756Z&x-oss-expires=3599&x-oss-signature-version=OSS4-HMAC-SHA256&x-oss-credential=LTAI****************/20241112/cn-hangzhou/oss/aliyun_v4_request&x-oss-signature=ed5a******************************************************"

	req, err := http.NewRequest(http.MethodGet, url, nil)
	if err != nil {
		log.Fatalf("failed to create GET request: %v", err)
	}

	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		log.Fatalf("request failed: %v", err)
	}
	defer resp.Body.Close()

	filePath := "C:/downloads/myfile.txt"
	file, err := os.Create(filePath)
	if err != nil {
		log.Fatalf("failed to create file: %v", err)
	}
	defer file.Close()

	n, err := io.Copy(file, resp.Body)
	if err != nil {
		log.Fatalf("failed to write object content: %v", err)
	}
	log.Printf("wrote %d bytes to %s\n", n, filePath)
}

When you include non-standard request headers in GetObjectRequest (such as RangeBehavior or RequestPayer), those headers become part of the signature. The requester must send the same headers with every GET request — otherwise OSS rejects the request with a signature error.

Step 1: Generate the URL with signed headers.

result, err := client.Presign(context.TODO(), &oss.GetObjectRequest{
    Bucket:        oss.Ptr(bucketName),
    Key:           oss.Ptr(objectName),
    RangeBehavior: oss.Ptr("standard"),
    RequestPayer:  oss.Ptr("requestpayer"),
},
)
if err != nil {
    log.Fatalf("failed to presign GetObject request: %v", err)
}
log.Printf("Method: %v\n", result.Method)
log.Printf("Expiration: %v\n", result.Expiration)
log.Printf("URL: %v\n", result.URL)

// Print signed headers so the requester knows which headers to include.
if len(result.SignedHeaders) > 0 {
    log.Printf("Signed headers (must be included in GET requests):\n")
    for k, v := range result.SignedHeaders {
        log.Printf("  %v: %v\n", k, v)
    }
}

Step 2: Download using the URL and the same signed headers.

curl:

curl -X GET "https://examplebucket.oss-cn-hangzhou.aliyuncs.com/exampleobject.txt?x-oss-date=20241113T093321Z&x-oss-expires=3599&x-oss-signature-version=OSS4-HMAC-SHA256&x-oss-credential=LTAI****************&x-oss-signature=ed5a******************************************************" \
-H "x-oss-range-behavior: standard" \
-H "x-oss-request-payer: requester" \
-o "myfile.txt"

Go:

package main

import (
	"io"
	"log"
	"net/http"
	"os"
)

func main() {
	url := "https://examplebucket.oss-cn-hangzhou.aliyuncs.com/exampleobject.txt?x-oss-date=20241112T092756Z&x-oss-expires=3599&x-oss-signature-version=OSS4-HMAC-SHA256&x-oss-credential=LTAI****************/20241112/cn-hangzhou/oss/aliyun_v4_request&x-oss-signature=ed5a******************************************************"

	req, err := http.NewRequest(http.MethodGet, url, nil)
	if err != nil {
		log.Fatalf("failed to create GET request: %v", err)
	}

	// These headers were signed into the URL — omitting them causes a signature error.
	req.Header.Set("X-Oss-Range-Behavior", "standard")
	req.Header.Set("X-Oss-Request-Payer", "requester")

	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		log.Fatalf("request failed: %v", err)
	}
	defer resp.Body.Close()

	filePath := "C:/downloads/myfile.txt"
	file, err := os.Create(filePath)
	if err != nil {
		log.Fatalf("failed to create file: %v", err)
	}
	defer file.Close()

	n, err := io.Copy(file, resp.Body)
	if err != nil {
		log.Fatalf("failed to write object content: %v", err)
	}
	log.Printf("wrote %d bytes to %s\n", n, filePath)
}

To use a custom domain name (CNAME) in the presigned URL, set the endpoint to your custom domain and enable CNAME mode when creating the client.

cfg := oss.LoadDefaultConfig().
    WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
    WithRegion(region).
    WithEndpoint("http://static.example.com").
    WithUseCName(true)

client := oss.NewClient(cfg)

result, err := client.Presign(context.TODO(), &oss.GetObjectRequest{
    Bucket: oss.Ptr(bucketName),
    Key:    oss.Ptr(objectName),
},
    oss.PresignExpires(10*time.Minute),
)
if err != nil {
    log.Fatalf("failed to presign GetObject request: %v", err)
}
log.Printf("Method: %v\n", result.Method)
log.Printf("Expiration: %v\n", result.Expiration)
log.Printf("URL: %v\n", result.URL)