## Write key-value pair with optional metadata

`client.KV.Namespaces.Values.Update(ctx, namespaceID, keyName, params) (*NamespaceValueUpdateResponse, error)`

**put** `/accounts/{account_id}/storage/kv/namespaces/{namespace_id}/values/{key_name}`

Write a value identified by a key. Use URL-encoding to use special characters (for example, `:`, `!`, `%`) in the key name. Body should be the value to be stored. If JSON metadata to be associated with the key/value pair is needed, use `multipart/form-data` content type for your PUT request (see dropdown below in `REQUEST BODY SCHEMA`). Existing values, expirations, and metadata will be overwritten. If neither `expiration` nor `expiration_ttl` is specified, the key-value pair will never expire. If both are set, `expiration_ttl` is used and `expiration` is ignored.

### Parameters

- `namespaceID string`

  Namespace identifier tag.

- `keyName string`

  A key's name. The name may be at most 512 bytes. All printable, non-whitespace characters are valid. Use percent-encoding to define key names as part of a URL.

- `params NamespaceValueUpdateParams`

  - `AccountID param.Field[string]`

    Path param: Identifier.

  - `Value param.Field[NamespaceValueUpdateParamsValueUnion]`

    Body param: A byte sequence to be stored, up to 25 MiB in length.

    - `UnionString`

    - `UnionString`

  - `Expiration param.Field[float64]`

    Query param: Expires the key at a certain time, measured in number of seconds since the UNIX epoch.

  - `ExpirationTTL param.Field[float64]`

    Query param: Expires the key after a number of seconds. Must be at least 60.

  - `Metadata param.Field[unknown]`

    Body param: Associates arbitrary JSON data with a key/value pair.

### Returns

- `type NamespaceValueUpdateResponse struct{…}`

### Example

```go
package main

import (
  "context"
  "fmt"

  "github.com/cloudflare/cloudflare-go"
  "github.com/cloudflare/cloudflare-go/kv"
  "github.com/cloudflare/cloudflare-go/option"
  "github.com/cloudflare/cloudflare-go/shared"
)

func main() {
  client := cloudflare.NewClient(
    option.WithAPIToken("Sn3lZJTBX6kkg7OdcBUAxOO963GEIyGQqnFTOFYY"),
  )
  value, err := client.KV.Namespaces.Values.Update(
    context.TODO(),
    "0f2ac74b498b48028cb68387c421e279",
    "My-Key",
    kv.NamespaceValueUpdateParams{
      AccountID: cloudflare.F("023e105f4ecef8ad9ca31a8372d0c353"),
      Value: cloudflare.F[kv.NamespaceValueUpdateParamsValueUnion](shared.UnionString("Some Value")),
    },
  )
  if err != nil {
    panic(err.Error())
  }
  fmt.Printf("%+v\n", value)
}
```

#### Response

```json
{
  "errors": [
    {
      "code": 1000,
      "message": "message",
      "documentation_url": "documentation_url",
      "source": {
        "pointer": "pointer"
      }
    }
  ],
  "messages": [
    {
      "code": 1000,
      "message": "message",
      "documentation_url": "documentation_url",
      "source": {
        "pointer": "pointer"
      }
    }
  ],
  "success": true,
  "result": {}
}
```