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# Argument parsing for Go
```go
import "github.com/alexflint/go-arg"
var args struct {
Foo string
Bar bool
}
arg.MustParse(&args)
fmt.Println(args.Foo, args.Bar)
```
```shell
$ ./example --foo=hello --bar
hello True
```
### Default values
```go
var args struct {
Foo string
Bar bool
}
args.Foo = "default value"
arg.MustParse(&args)
```
### Marking options as required
```go
var args struct {
Foo string `arg:"required"`
Bar bool
}
arg.MustParse(&args)
```
### Positional argument
```go
var args struct {
Input string `arg:"positional"`
Output []string `arg:"positional"`
Verbose bool
}
arg.MustParse(&args)
fmt.Println("Input:", input)
fmt.Println("Output:", output)
```
```
$ ./example src.txt x.out y.out z.out
Input: src.txt
Output: [x.out y.out z.out]
```
### Usage strings
```shell
$ ./example -h
usage: [--verbose] [--dataset DATASET] [--optimize OPTIMIZE] [--help] INPUT [OUTPUT [OUTPUT ...]]
positional arguments:
input
output
options:
--verbose, -v verbosity level
--dataset DATASET dataset to use
--optimize OPTIMIZE, -O OPTIMIZE
optimization level
--help, -h print this help message
```
### Options with multiple values
```
var args struct {
Database string
IDs []int64
}
arg.MustParse(&args)
fmt.Printf("Fetching the following IDs from %s: %q", args.Database, args.IDs)
```
```shell
./example -database foo -ids 1 2 3
Fetching the following IDs from foo: [1 2 3]
```
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