Finish the Day Two post
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Lewis Dale 2024-04-30 07:27:14 +01:00
parent 5eab7bcb9d
commit 5aa099665c
2 changed files with 67 additions and 5 deletions

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---
title: ""Learning Go: Day Two"
title: "Learning Go: Day Two"
date: 2024-05-02T08:00:00.0Z
tags:
- tech
@ -27,8 +27,70 @@ Fairly straightforward, right?
## Importing and running the code
So, I can't just do `import "maths"`, because that doesn't seem to resolve. Instead, I have to refer to my entire module name, and then append the path to it:
```go
import "lewisdale.dev/learn-go/maths"
```
So now I should be able to use my imported module and call `maths.multiply`, right?
```go
func main() {
fmt.Println(sayHello())
num := maths.multiply(2, 5)
fmt.Printf("2 * 5 = %d\n", num)
}
```
```bash
go run main.go
> ./main.go:16:15: undefined: maths.multiply
```
## Wait, what?
So, it turns out in Go, there's no explicit export keyword. Instead, if you want a function to be exported [you have to capitalise the first letter](https://go.dev/tour/basics/3). Lowercase functions are implicitly private.
```go
// maths.go
package maths
func Multiply(a, b int) int {
return a * b
}
```
And then we can do
```go
// main.go
func main() {
fmt.Println(sayHello())
num := maths.Multiply(2, 5)
fmt.Printf("2 * 5 = %d\n", num)
}
```
As a useful extra, the Go plugin on VS Code[^2] even organised my imports into one `import ()` statement:
```go
// main.go
package main
import (
"fmt"
"lewisdale.dev/learn-go/maths"
)
```
## The vendor directory
[^1]: Yes, maths, not math
When I was looking up how to create and import modules, I did find [this useful StackOverflow comment](https://stackoverflow.com/a/45813698) that mentions that Go > 1.5 has support for a `vendor` directory, that allows you to put code inside a `vendor` directory, and Go will lookup the package without requiring the local module prefix.
I'm not going to use this, just because I'm probably going to reinvent the wheel a few times over the course of this series and I don't know the standard library well enough[^3] to trust myself to not accidentally tread all over it, but it's good to know it's there.
[^1]: Yes, maths, not math
[^2]: It was less helpful when it kept auto-deleting my import before I did the export though, had to use Vim just to make my point.
[^3]: Or like, at all.

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--color-secondary: var(--color-neutral-800);
--color-decoration: var(--color-amber-200);
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--color-subtle: var(--color-neutral-300);
--color-disabled: var(--color-neutral-400);
--color-accent: var(--color-zinc-600);
@ -60,7 +60,7 @@
--color-primary: var(--color-neutral-200);
--color-secondary: var(--color-neutral-800);
--color-decoration: var(--color-amber-200);
--color-subtle: var(--color-zinc-400);
--color-subtle: var(--color-neutral-300);
--color-disabled: var(--color-neutral-400);
--color-accent: var(--color-zinc-400);
--color-callout-bg: var(--color-slate-800);
@ -71,7 +71,7 @@
--color-primary: var(--color-neutral-200);
--color-secondary: var(--color-neutral-800);
--color-decoration: var(--color-amber-200);
--color-subtle: var(--color-zinc-400);
--color-subtle: var(--color-neutral-300);
--color-disabled: var(--color-neutral-400);
--color-accent: var(--color-zinc-600);
--color-callout-bg: var(--color-slate-800);