# Custom Package

Let's write a package to import and use in `hellogo`.

Create a sibling directory at the same level as the `hellogo` directory:

```bash
mkdir mystrings
cd mystrings
```

Initialize a module:

```bash
go mod init {REMOTE}/{USERNAME}/mystrings
```

Then create a new file `mystrings.go` in that directory and paste the following code:

```go
// by convention, we name our package the same as the directory
package mystrings

// Reverse reverses a string left to right
// Notice that we need to capitlize the first letter of the function
// If we don't then we won't be able access this function outside of the
// mystrings package
func Reverse(s string) string {
  result := ""
  for _, v := range s {
    result = string(v) + result
  }
  return result
}
```

Note that there is no `main.go` or `func main()` in this package.

`go build` won't build an executable from a library package. However, `go build` will still compile the package and save it to our local build cache. It's useful for checking for compile errors.

Run:

```bash
go build
```