# Go (/en/docs/guide/getting-started/go)
go get and go — embedded WebAssembly, no cgo, cross-compilation preserved.
*For: developers*
## Installation [#installation]
```bash
go get github.com/x-haose/x-iztro/go/iztro
```
The package embeds a WebAssembly module compiled from the core library (`wasm32-wasip1`) and calls
into it through [wazero](https://wazero.io), a runtime implemented in pure Go.
Which means: **no cgo, no Rust toolchain on the machine, and cross-compilation still works**.
wazero's compiler backend covers amd64 and arm64 only; other architectures fall back to the
interpreter — slower, same results.
A single wasm instance cannot be used concurrently, so the package keeps an instance pool (capped at
`GOMAXPROCS`). Calls from multiple goroutines are not serialized against each other and run in
genuine parallel.
The first call has to compile the wasm module. The compiled artifact is cached on disk (under
`os.UserCacheDir()`), so only the very first run costs \~200ms; after that the first call in each
process costs \~30ms. If you want a service's first request to take the hot path, call
`iztro.Warmup(ctx)` once at startup. On the hot path a chart — including JSON encoding, decoding and
memory copies — is on the order of 0.5ms.
## Charting [#charting]
```go
package main
import (
"fmt"
"log"
"github.com/x-haose/x-iztro/go/iztro"
)
func main() {
// the fifth argument is the chart language; "zh-CN" is what the other
// pages default to, "en-US" gives an English chart
chart, err := iztro.BySolar("2000-8-16", 2, iztro.GenderFemale, true, iztro.LanguageEnUS, nil)
if err != nil {
log.Fatal(err)
}
fmt.Println(chart.SolarDate) // Gregorian date
fmt.Println(chart.LunarDate) // lunar date
fmt.Println(chart.ChineseDate) // the four pillars
fmt.Println(chart.Time, chart.TimeRange)
fmt.Println(chart.Sign, chart.Zodiac)
fmt.Println(chart.Soul, chart.Body) // soul star, body star
fmt.Println(chart.FiveElementsClass)
}
```
```text
2000-8-16
二〇〇〇年七月十七
geng chen - jia shen - bing woo - geng yin
Tiger hour 03:00~05:00
leo dragon
rebel scholar
wood 3rd
```
`LunarDate` is the one field that stays in Chinese in an English chart: the lunar date is written
with Chinese numerals, and `二〇〇〇年七月十七` is the 17th day of the 7th lunar month, 2000.
`ChineseDate` is the four pillars romanized in pinyin — `geng chen` is 庚辰, `bing woo` is 丙午.
The last argument is a `*Config`; pass `nil` for the defaults. `gender` and `language` are the named
types `iztro.Gender` / `iztro.Language` (`iztro.GenderFemale`, `iztro.LanguageEnUS`; string literals
still work). Chart from a lunar date with `ByLunar`: where `BySolar` takes `fixLeap`, this takes a
three-way `iztro.LeapMonth` (`NotLeapMonth` / `LeapMonthKeep` / `LeapMonthFixed`), so one argument
says how the leap month is handled:
```go
iztro.ByLunar("2000-7-17", 2, iztro.GenderFemale, iztro.NotLeapMonth, iztro.LanguageEnUS, nil)
```
Every entry point has a `*Context` variant (`BySolarContext`, `ByLunarContext` and so on), where
`ctx` cancels the wait for a pooled instance.
## Error handling [#error-handling]
Failures always come back as `*iztro.Error` carrying a machine-readable `Code`; match them by
category with `errors.Is`:
```go
_, err := iztro.BySolar("2000-13-1", 2, iztro.GenderMale, true, iztro.LanguageEnUS, nil)
if errors.Is(err, iztro.ErrInvalidDate) {
var e *iztro.Error
errors.As(err, &e)
fmt.Println(e.Code, e.Message)
}
```
```text
invalid_date invalid solar date '2000-13-1': month must be within 1-12
```
See [Error handling](/en/docs/guide/guides/errors).
## Next [#next]
The example above only touches the charting entry point. The full API — locating the twelve palaces,
star predicates, flying stars, horoscopes, the star-placement module, data tables and translation —
lives under **[Go API](/en/docs/go)**, where every exported function, type and method has its own
entry with real run output and edge-case notes.