Google Cloud Storage

The gcs driver wraps cloud.google.com/go/storage’s *storage.Client.

When to use it

• Object storage on Google Cloud.
• You want native pre-signed URLs and resumable uploads.

Install

go get github.com/gobeaver/filekit/driver/gcs
go get cloud.google.com/go/storage

Construct

import (
    "context"
    "time"

    "cloud.google.com/go/storage"
    "github.com/gobeaver/filekit/driver/gcs"
)

ctx := context.Background()

client, err := storage.NewClient(ctx) // uses GOOGLE_APPLICATION_CREDENTIALS
if err != nil {
    panic(err)
}
defer client.Close()

fs := gcs.New(client, "my-bucket",
    gcs.WithPrefix("uploads/"),
)

_, _ = fs.Write(ctx, "doc.pdf", reader)

url, _ := fs.SignedURL(ctx, "doc.pdf", 30*time.Minute)
_ = url

Options

• gcs.WithPrefix(prefix string) — prepended to every object name. A trailing / is added if missing.

Credentials

Credentials are handled by the GCS SDK, not filekit. Standard mechanisms work: GOOGLE_APPLICATION_CREDENTIALS pointing at a service-account JSON, workload identity, gcloud auth application-default login, or option.WithCredentialsFile(...) passed to storage.NewClient.

For pre-signed URLs to work, the client needs credentials that include a private key — that means a service-account JSON, not metadata-server-only auth, unless you configure iamcredentials.signBlob.

Capabilities

Interface	Implemented	Notes
FileSystem	yes
CanCopy	yes	native CopierFrom
CanMove	yes	copy + delete
CanSignURL	yes	SignedURL, SignedUploadURL
CanChecksum	yes	uses object MD5/CRC32C from GCS metadata when available
CanWatch	yes	polling-based (default 30 s)
ChunkedUploader	yes	maps to GCS resumable uploads
CanReadRange	no	not implemented in this driver yet

Quirks

• WriteResult.Checksum after a write is GCS’s MD5 (hex-encoded), with ChecksumAlgorithm = ChecksumMD5. GCS does not return SHA-256.
• WithOverwrite(false) (the default) issues an extra Object.Attrs call before uploading; this costs one round trip.
• Directory existence is checked by listing with a prefix.