Download a file (Go SDK V1)

Prerequisites

Before you begin, ensure that you have:

• An OSS bucket with versioning enabled

• The oss:GetObject permission attached to your RAM user. See Attach a custom policy to a RAM user

• The OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables set with your access credentials. See Configure access credentials

Usage notes

• The examples use the public endpoint for the China (Hangzhou) region. To access OSS from another Alibaba Cloud service in the same region, use the internal endpoint instead. See Regions and endpoints.

• To create an OSSClient instance using a custom domain or Security Token Service (STS), see Configure OSSClient instances.

Download an object by version ID

The following example downloads a specific version of an object and reads the version ID from the response header.

package main

import (
	"log"
	"net/http"

	"github.com/aliyun/aliyun-oss-go-sdk/oss"
)

func main() {
	// Load access credentials from environment variables.
	// Set OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET before running.
	provider, err := oss.NewEnvironmentVariableCredentialsProvider()
	if err != nil {
		log.Fatalf("Failed to create credentials provider: %v", err)
	}

	// Create an OSSClient instance.
	// Replace <yourEndpoint> with the endpoint for your bucket's region,
	// for example: https://oss-cn-hangzhou.aliyuncs.com
	// Replace <yourRegion> with the region ID, for example: cn-hangzhou
	clientOptions := []oss.ClientOption{
		oss.SetCredentialsProvider(&provider),
		oss.Region("<yourRegion>"),
		oss.AuthVersion(oss.AuthV4),
	}
	client, err := oss.New("<yourEndpoint>", "", "", clientOptions...)
	if err != nil {
		log.Fatalf("Failed to create OSS client: %v", err)
	}

	bucket, err := client.Bucket("<yourBucketName>")
	if err != nil {
		log.Fatalf("Failed to get bucket: %v", err)
	}

	// Download a specific version of an object.
	// Set the full path of the object, excluding the bucket name.
	// If the version ID belongs to a delete marker, OSS returns 405 Method Not Allowed.
	// If the current version is a delete marker and no version ID is specified, OSS returns 404 Not Found.
	objectName := "<yourObjectName>"
	objectVersionId := "<yourObjectVersionId>"

	var retHeader http.Header
	_, err = bucket.GetObject(
		objectName,
		oss.VersionId(objectVersionId),
		oss.GetResponseHeader(&retHeader),
	)
	if err != nil {
		log.Fatalf("Failed to get object: %v", err)
	}

	// Print the x-oss-version-id returned in the response.
	versionId := oss.GetVersionId(retHeader)
	log.Printf("x-oss-version-id: %s", versionId)
}

Replace the following placeholders with your actual values:

How versioning affects GetObject

When you call GetObject on a versioning-enabled bucket:

References

• Complete sample code on GitHub

• GetObject API reference