Go SDK - Config values - Westyx Nexus

Changed in v0.11.0. GetConfig returns the decoded JSON value. The type mapping is:

JSON	Go
string	`string`
number	`json.Number`
boolean	`bool`
object	`map[string]any`
array	`[]any`
null	`nil`

raw, ok := client.GetConfig("max_items")
if !ok {
    // key is not in the cache
}
limit, err := raw.(json.Number).Int64()

Why numbers are `json.Number`

Because float64 cannot hold every integer a config value might be. encoding/json decodes a JSON number into float64 when the destination is an any, and float64 has a 53-bit mantissa. Above 2^53 it starts rounding: a snowflake id, a Stripe amount in minor units, a nanosecond timestamp all come back as a different number, and nothing anywhere reports a problem. 9007199254740993 becomes 9007199254740992. json.Number is the exact decimal text the backend sent, converted only when you ask:

n := raw.(json.Number)
n.String()   // "9007199254740993" - exactly what the server stored
n.Int64()    // 9007199254740993, nil
n.Float64()  // 9.007199254740992e+15, nil - lossy, and you chose it

Int64 returns an error for a fractional value or one outside int64’s range, so a mistake surfaces as an error instead of a wrong number. This is the same decision the other Nexus SDKs make in their own idiom: the SDK owns the representation of a config value rather than inheriting a lossy one from whatever its JSON library happened to reach for.

Typed reads with `GetConfigAs`

Asserting and converting by hand gets tedious, so decode into your own type instead:

type Endpoint struct {
    Host string `json:"host"`
    Port int    `json:"port"`
}

endpoint, err := nexus.GetConfigAs[Endpoint](client, "db.endpoint")
if err != nil {
    return err
}

It works for scalars too:

limit, err := nexus.GetConfigAs[int64](client, "max_items")
hosts, err := nexus.GetConfigAs[[]string](client, "allowed_hosts")

GetConfigAs is a package-level function rather than a method because Go methods cannot have type parameters. Decoding happens from the exact bytes the backend sent, not from the already decoded value, so your json tags, embedded types and custom UnmarshalJSON all behave exactly as they would if you had unmarshalled the response yourself - and no precision is lost on the way through.

Returns	When
`ErrConfigNotFound`	The key is not in the cache. Check with `errors.Is`.
a wrapped decode error	The stored value does not fit `T`.

Mutation safety

GetConfig and GetAllConfigs return deep copies of object and array values, so a caller mutating a returned map[string]any or []any cannot reach into the shared cache or race a background refresh. Scalars are copied by value.

Reading everything at once

for key, value := range client.GetAllConfigs() {
    fmt.Printf("%s = %v (%T)\n", key, value, value)
}

Public (wxp_) keys receive the same configs and flags a secret key does. What they do not receive is secrets, which are absent from the sync response entirely.

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Go SDK - Config values

Why numbers are `json.Number`

Typed reads with `GetConfigAs`

Mutation safety

Reading everything at once

Next

​Why numbers are json.Number

​Typed reads with GetConfigAs

​Mutation safety

​Reading everything at once

​Next

Why numbers are `json.Number`

Typed reads with `GetConfigAs`

Mutation safety

Reading everything at once

Next