# Configuration

This page covers go-scheduler's scheduler settings, per-task options, and the runtime defaults for logging and the worker pool.

## Scheduler Settings

```go
type Config struct {
	Location *time.Location
}
```

| Field | Default | Effect |
|---|---|---|
| `Location` | `time.Local` | Timezone used to compute the next fire time of cron expressions and descriptors |

```go
loc, err := time.LoadLocation("Asia/Taipei")
if err != nil {
	log.Fatal(err)
}

c, err := core.New(core.Config{Location: loc})
if err != nil {
	log.Fatal(err)
}

if _, err := c.Add("30 9 * * 1-5", func() error {
	return sendReport()
}, "weekday report"); err != nil {
	log.Fatal(err)
}
```

`30 9 * * 1-5` fires at 09:30 Monday to Friday in `Asia/Taipei` time.

The package reads no environment variables or configuration files.

## Task Options

`Add` identifies variadic arguments by type, in any order:

```go
func (c *cron) Add(spec string, action interface{}, arg ...interface{}) (int64, error)
```

| Type | Sets | Notes |
|---|---|---|
| `string` | Task description | Logged by the dependency worker |
| `time.Duration` | Execution limit | Not a start delay; `0` means no limit |
| `func()` | Timeout callback | Called only when the execution limit is exceeded |
| `[]core.Wait` | Prerequisites | Action must be `func() error` |
| `[]int64` | Prerequisites (deprecated) | Each ID becomes `Wait{ID: id}` with the `Stop` policy |

When the same type is passed more than once, the last `string` / `time.Duration` / `func()` wins, while `[]core.Wait` and `[]int64` accumulate.

```go
_, err := c.Add("*/10 * * * *", func() error {
	return syncInventory()
}, "inventory sync", 2*time.Minute, func() {
	log.Println("inventory sync exceeded 2m")
}, []core.Wait{
	{ID: authID, State: core.Stop},
	{ID: cacheID, State: core.Skip},
})
if err != nil {
	log.Fatal(err)
}
```

## Dependency Settings

| Field | Value | Effect |
|---|---|---|
| `ID` | Prerequisite task ID | Dependent task fails when the ID does not exist |
| `State` | `core.Stop` (default) | Dependent task fails when the prerequisite fails |
| `State` | `core.Skip` | Failed prerequisite is ignored |
| `Delay` | Any | Currently not applied; the wait limit is fixed at 1 minute |

## Runtime Defaults

| Item | Value | Source |
|---|---|---|
| Logger | syslog (`LOG_INFO\|LOG_LOCAL0`, tag `goCron`) in JSON | `core/instance.go` |
| Logger fallback | stderr text, Info level | When syslog cannot be opened |
| Dependency workers | `runtime.NumCPU()`, or 2 when CPUs ≤ 2 | `core/depend.go` |
| Wait queue capacity | 1024 | `core/depend.go` |
| Dependency poll interval | 1ms | `core/dependManager.go` |
| `@every` minimum interval | 30 seconds | `core/schedule.go` |

None of these values can be changed by callers.

See [Task Dependencies](/core-concepts-dependencies) and [Timeouts](/core-concepts-timeouts) for runtime behavior.